I've been drawing simple tattoo designs for people off and on for a few years now. I like to keep my original drawings for obvious reasons and I've been using a scanner/printer to give out copies. So I made up my mind and made an inexpensive and attractive light table. I aimed for a lap or table top sized box, something easy to plug in, use, and stow away. I believe I've succeeded. :D
Step 1: Choosing a Size
I wanted to build a table that could accommodate regular 8X11 sheet and larger sketch sheets. This made choosing the plexi a relatively easy choice. After I chose the 18X24" size ($8) I wasn't sure if it was going to be stiff enough to draw on(it is, just fyi) but had an idea to cut it in half, double up the panes and not trim it down, keeping it at a healthy 12X18. This also had an added benefit of being able to add tracing paper for diffusion between the panes of plexi.
To cut it I used a band saw. I cut it a little wider (a FRACTION!) so it fit snug.