I first start as many binders do when making a box with a series of measurements. Height, width and depth. Then make up small compensation pads for the lining material and start chopping. I cut the walls and then line the board with 240 gsm water colour paper, trimming the water colour paper to leave a flange the same width as the board (in this case 2mm ) Making a half lap joint.
I consider it a stronger joint than just butting the board together and saves on having to masking tape all the components together.