Commercially, I would guess it’s done with a shaper, but I have done it myself with a jig I made for my table saw. Basically, I have a box that I clamp to the fence that lets me slide my work side to side across the blade. I have two wedges that are attached to each other about 8 inches apart ( I started out using tree-falling wedges, but ended up cutting wood ones). The wedges sit with the thick end toward the fence, and I put the board on top and slowly slide it sideways across the blade, stopping when I hit the fence (which is measured so each cut ends at the same point). The wedges make it possible to make that angled cut. I only make boxes out of pine, which is very soft but I still make about 4 shallow (1/8”-3/16”) cuts. Anything deeper is very hard on saw blades and on the bearings. Now, my disclaimer- unless you are a very experienced woodworker I would not suggest this- just attach handles. I am extremely cautious to keep everything away from the blade, and take every precaution. I’ve been working with power tools since I was about 8 and fully understand the possibility of kickback, binds, etc. Please, don’t attempt to do it this way if you don’t have extensive woodworking experience!