Maya’s tiny house has three different corner trim profiles; an outside 90 degree, an outside 115 degree, and an inside 115 degree. Fabricating these in advance of installation takes a little more time but produces a much higher quality result.  Anyone who has ever made an 8 foot long corner joint will tell you that it is very easy to screw up if you do not have precisely cut miters. To ensure accurate cuts we used the setup shown below to hold our boards flush to our table saw fence and flush to the table (on both sides of the board). Glue up clamping was done using a butterfly method. Two boards are placed parallel to each other with their mitered outside edges just touching. A piece of duct tape is run down the entire length of the edge. After the adhesive is applied to the mating surfaces, the joint is “folded” along the tape line into the final position and held in this position with additional duct tape.