Dan, everything is mortise and tenon. I could take a photo of where a leg joins the bottom of the seat, but not sure that'll really help much. I'll try to explain concisely. All I did was drill the mortises at an 11-15 degree angle (builders preference) and then turn the tenons to fit the mortises. With that, the shoulders of the tenons need to be cut so they'll match the 11-15 degree mortise. Otherwise the stool is likely to develop quite a bit of laxity, which could lead to the stool collapsing at an inopportune time. The stretchers/rungs go into the legs the same way, but these mortises also must be drilled at an angle to complement the angle of the legs, otherwise the stretchers won't be horizontal. Hope that answers your questions, and hope you have a easier time trying to assemble all that during glue-up.
I used to run with scissors.... guess I graduated.