Yes, I agree, Bruce Red, with what you said, BUT. Lemme address points above one by one so you and others can make a fair judgement.
Consider this a tutorial of sorts for first time slotters.
1. If you double the band over on itself so there is about 3/4 inch of double over, and insert a peg in the bend of the band, called the "match stick" method (twig from a tree in an extreme situation would work) into the bend or loop, then holding the bend with the thing in it between thumb and forefinger, stretch and insert down into the slot. IF the slot isn't too wide or too thin, it will hold without fail. Now let's go over some "ifs".
2. What saw do I use? I cut my slots with an ordinary hack saw, that's a pretty thin blade, carefully, with masking tape over the tip -with a line drawn on it- on both sides of the fork where the cut goes. I make the first few saw motions to get the cut started straight and carefully check it on BOTH sides to make sure all is working as planned. Then I make several more saw motions and check again, both sides and so on until I am done with the slot..then do the other fork. I mount the frame in a rather large vise with a soft cloth over the frame handle to make sure the vise doesn't mar it...and close the vise jaws with common sense tightness..not too tight so as to mar the handle, not too loose so the frame moves or slips. You can play with an ordinary piece of wood to make a few test slots so you can familiarize yourself before you go head long into a frame.
3. I use a caliper to mark a dot on the masking tape so both slots are in the same position on the fork tips.
4. Now let's address what Bruce said about weakening the tips. I make my fork tips with enough material that a slot won't make it so weak it would break. What is "enough material"? That depends on what the fork tip is made of of course but if the frame is made of decent material, and we hope it is (!) then a slot which leaves 1/8th of material on each side of the slot is the minimum I would permit..best to leave 3/16ths of an inch or so. And of course the fork geometry plays a factor here..note my forks (see the collection photo posted today by "Susi", my wife's gallery. Note my forks are pretty beefy or made of steel in some cases.
5. Finishing the slot and widening it to spec is easy but done with care and doesn't take long at all. I use first 80-100 grit paper, an inch wide by four inch long "belt" of it cut from a larger piece of sand paper. I slip this through the slot and work it back and forth on each side of the slot carefully and thoroughly to do two things. First, to obviously sand off saw marks and second to round the corners of the slot so they don't cut into the band. Next, after the slot is widened a bit I fold the paper so it is twice as thick and work it gently into the slot again to widen it just a bit. Next I go to 200 grit and repeat, being careful to not widen the slot a heck of a lot but to smooth the inside and to round the edges a bit more. Next, 300 grit briefly and that's it.
So how do you know if the slot is too slim or too wide? Remember I suggested to practice slotting on scrap wood. That way you can sand, try a band attachment, if it's too slim, widen it a bit with sand paper until a doubled over band will, with peg, stay in place and barely fit when stretched. After you've made several practice slots THAT WORK, then you are ready for your frame. If you are making a natty, use a branch to practice on. If not, use a piece of scrap from the "U" cut out of the fork void. Yes, beads of sweat will form on your forhead and yes it's going to have to go slowly. I've made many slots and believe me it's 100% concentration and yes, slowly...checking both sides of the slot frequently.
And make sure you put masking tape on the inside and outside of the fork tip to draw your cut line on both sides...that way you can check to make sure the slot is cutting correctly and not slanted.
I cut both slots about half way, then put the saw into BOTH OF THEM and saw them the rest of the way, one sort of guides the other and go SLOWLY a few saw motions at a time. You can cut each individually to a point but to get a flat bottom you need to cut both at the same time else it gets a little clumsy trying to move a saw without banging the other fork on the inside of the "U".
I use a new hack saw blade, old ones want to cut in a slant because one side of the teeth is usually worn more than the other causing a curved cut. Use the thinnest you can get, that way if you goof a little, no matter, the widening process will eat up the goof.
Top slots with the hole at the bottom are tougher...for OTT frames and I don't use that method. Hats off to the precision guys who can drill and slot OTT top slots without issue!!! I'm not an OTT shooter thank goodness.
What if you want to use double bands then change to single bands, say if you want to hunt and use righteous ammo and pull lbs, you might want to use double 20mm TBG but for practice only a single band. Fine. Make the slots wide enough to fit the double bands and when it's time to change to singles, just save a few fragments an inch long of broken band and use them as shims, to make the stretched single band equal to the double band in thickness. It's simple. All my frames are slotted for double bands and mostly I use singles with shims.
I used to NOT use the peg and some slipped, rarely, but slipped..then I started using pegs exclusively, why not? It guarantees the bands won't slip.
Wham-o's "Sportsman" board cut used slots and so have many other vintage frames I've owned as a kid.
One post recently had a groove cut in the natural fork tip AND a slot to appease both methods. I tied bands as a kid and also used slots, and same-same a few years ago..finally deciding slots rule.
What if you mess up?
You can fill the messed up slot with a slim insert of the same material using epoxy and re slot it..it's not going to show much if at all, depends on how bad the goof was. Have I ever messed up a slot? Yes, twice and patched it and it was invisible in the finished frame.
Other than slotting, how can I get away from tieing?
Thumb screw clips or screw driver type or coin width slotted screws with clips are also dandy ways to anchor bands but they look "equipmenty" to me and are one more thing to fuss with so I don't use mechanical clips or screws of any sort...but they work, are fast to change bands and hold well.
Nathan's (Simple Shot) and Bill Hays' clips (Pocket Predator) work fine...it is your call however. YSYEO has a dandy method of using Chicago screws/bolts...he has a vid on this on youtube...if you can't find it PM you'llshootyoureyeout and he'll give you a link.
For tubes, Byudsai has a dandy no tie method he invented...PM him for the links..you can also use holes and BBs or bearings or shot of any metal which are the right diameter and golf tee points to plug the free end of the tube so it won't pull out.
I think the fear of messing up a nice frame is a leading cause for not cutting grooves or slots, many frames are slick smooth and with no anchor at all for that reason...aesthetics and fear. I'm a function nut so aesthetics and I don't get along much yet the slot is absolutely the cleanest and most non interrupting method of attaching a band to a fork.
Note also that the loose short end of the band coming out of the slot is positioned so it pads the actual band rather than flop flop around and ruin your sight picture. It's held tight against the fork tip by the stretched band over it. See the drawing below please. Click on the images to enlarge them..sorry for the rather low quality on the bottom image...dunno what happened.