I used my Porter Cable biscuit joiner for the top on the bench! Worked great. I considered doing a mitered corner thing like that, but I was worried about expansion of the inner field breaking the joints... If I do another one, I'll consider doing a plywood seat with mitered hard wood border like that. Especially if the user plans on using a cussion on it. Also, if I were to do a true face frame cabinet, vs a bench with legs, I would probably pocket screw the face frame together, followed by biscuits to locate it on the carcase.
