Frame. Pry off enough pallet slats to make a wall on top of the plywood. They will form a basin and support the windshield; note that a wide, shallow still is a more efficient than a tall, deep one. (Incidentally, one pallet slat's width is the perfect height.)
Body. On one face of the plywood, screw and glue pallet slats all the way around the edge into a tight-fitting border.
Basin. Apply caulk to the inside of the plywood and pallet slats, ensuring all surfaces and joints are sealed. You want the inside of the still to be a waterproof basin. (I found that scraps of wood and paper made light work of spreading a uniform layer of caulk.)
Gutter. The gutter will run inside the still (along a longer wall of its basin), collect condensed vapor dripping off the windshield, and drain the fresh water through a hole in the basin's wall. Start by sawing the copper pipe to fit a long edge of the windshield, plus a couple of inches extra (the extra will poke through the wall). Measure the pipe against the longer basin wall, and mark the pipe where it will pass through. Snip the pipe down its length with the shears, stopping at the wall mark. Saw halfway through the pipe perpendicular to the slit you just made and not across it (the cut should stop at the slit). Use the box cutter to score the length of the pipe opposite the slit, stopping at the rounded end of the pipe. Using the pliers, bend the flap you just created all along the length of the score. What remains should be an open trough of copper with a flap down its length and one rounded, un-slit end. Use two extra pallet slats to hammer the flap into a flat lip.
Drain. Drill a copper pipe–sized hole through one of the short sides of the caulked basin, near the top of the wall. Poke the rounded end of the pipe into the hole, and set the flat lip of the pipe along the top of the longer basin wall.
Faucet. Opposite the gutter wall, drill a hole about a half inch from the top of the still. Jam the faucet into the hole so that the business end of the faucet is pointing up, and the pipe end extends into the still. Foul water will get poured through the open faucet into the basin.
Glass. Lay the windshield on top of the basin. Use duct tape to hold it in place, and seal any gaps between the glass and basin with caulk, then with a layer of tape on top, and then more caulk. This seal is very, very important, so take your time and make sure nothing can leak out between the glass and the wall.
Hose. Run scrap hose from the protruding copper pipe, down a slight slope, and into a clean collection vessel of your choice. Seal the connections between the pipe, the hose, and the collector with duct tape.
Sealant. Caulk every nook and cranny, and allow at least a full day to cure. The whole assembly needs to be vapor-tight or it will not work. A simple test for vapor-tightness: Close the faucet, and blow as hard as you can into the copper pipe. Can you blow freely without much resistance? Then the still is leaky; lay more caulk, let it cure, and try again. Does blowing get harder and have you seeing little black spots dancing in your field of vision? The bad news: You've killed some brain cells. The good news: Your still is ready to use.