I recently made a mitered frame to replace a pile of textbooks, using some prefinished plywood scrap.
Rather than making dimensioned drawings in CAD or by hand, I wrote an ordering of table saw setups and cuts that would yield a well fitting box, and the dimensions could be chosen as I worked with the physical material.
Decent miters, courtesy of a digital miter gauge. The face turned out better than the back.
Rundong Tian 2017