The basic stack-up is like this:
A thin craft foam on the bottom, a stiffener (thin plastic) in the middle, and another thin layer of craft foam on top.
A thicker (~20mm) foam with cutouts for various wrench sizes
Step 1: Obtain all supplies and tools
hot glue gun
wrenches to put into case
plastic stiffener (to put in-between craft foam, for backing)
Small pieces of plastic which labels can be engraved onto
hot glue stick
One of the most important tools in this project is the laser cutter, it is used to create the custom foam cutouts. I spent a long time choosing a case, and eventually I bought a case on amazon for ~$20 (http://www.amazon.com/gp/product/B000TMFNLK/ref=oh_o02_s00_i00_details). The inner dimensions of the case are approximately: 395mm wide by 290mm tall by 40mm deep on the bottom, and 25mm deep on the top. I already had 1.5mm craft foam in several colors available, along with 40mm charcoal colored foam. I used some two-layer engravable plastic for the label under each wrench.