The uprights and bottom are 2x3's. That 'U' shape is then screwed to another piece that I use to clamp to a bench. All I did was use 1/2" conduit clamps on top to hold the axle. I originally made it for MX wheels, but it worked ok for the Z wheels too. Measure (with spacers) the width of the rear hub, that will determine the length of the bottom piece. If the front is narrower, you might have to add homemade spacers (I've used scrap pieces of wood too) so the wheel doesn't move around so much on the stand. When you get a wheel mounted, mark a spot on an upright at the corner of the rim. Then drill a hole slightly smaller than 1/4" and thread in a piece of 1`/4" threaded rod. Use this as a reference point. If you use the corner of the rim you can use the same pointer for the side to side and up/down movement. You need a different hole for the front wheel.
This stand will give you a solid baseline when you build the wheels. To fine tune them, install the wheel on your bike and fasten an old pencil or something to your fork or swingarm to get the rim 100%.
A couple tips:
First off, mark the inside of the rim with a marker or something. This is your reference point so you know where you started while truing.
Once you have the wheel laced, tighten all the nipples first so there's like 3 threads left on the spokes. Then tighten flush to the last thread. Move around the wheel in a star fashion for equal tightness. Then you can start truing radial (up/down) first. Once you have the rim true you can true for axial (side to side). Once that is done, go over all the spokes by tapping them and make sure they all "ring" a bit. Any "thud" spokes are too loose. Double check for true once more, then mount to your bike and check one last time.
After you ride the bike check the spokes 2-3 more times. Then the wheel should be "set" and you'll just have to go over the spokes with normal intervals (1000 miles or so).