I made mine a different way for 1" box joint. My way is very Dangerous (will not attempt it again) using an original template with a gap between template and the work piece and using a large router bit with 5/8 collar.
So after few attempts and managing to make one 1-1/8 on 7/8 = 1” joints) , I realized given my track record with accidents, how lucky I was I didn’t end up with another gash above my eye.
So here’s an easier and less insane way of trying.
http://www.melevsreef.com/acrylics/teeth.html
Although I must say that even though the completed work pieces look perfect, each individual pin and gap must be measured with caliper and also tested. Even a small off-set like 1/32 will make the joints useless.