Step 1: Design
Anyway, you need to draw it out on something sturdy to actual size after you have made a final design decision. I used a piece of wood, cardboard would work. Then you need to decide what your measurements will be. Just saying it right now, simple is safe. I used measurements in increments of 1 half inch. That is to say that I never made a measurement that was not a multiple of 1/2. This helped out a ton when making the frame.