Place two 96-inch studs on the ground, parallel to each other, 96 inches apart.
Place two 90-inch studs on the ground, parallel to each other, 96 inches apart.
Place two 84-inch studs on the ground, parallel to each other, 96 inches apart.
Place one 96-inch stud perpendicular across the top of all three sets. Using a screw gun and 3-inch screws, screw the perpendicular studs to the parallel studs at the corners. You should now have three individual frames.
Use two assistants to stand the three frames up, graduating in height from tallest to shortest, 96 inches apart. Hold one 16-foot stud horizontally flat against the sides of all three frames, 36 inches up from the ground. Use the screw gun to screw it to the sides of the frames, securing them together. Hold another 16-foot stud horizontally and flush with the top of all three frames, it will angle down slightly. Screw it to the frames with the screw gun. Do both sides of the booth the same.
Walk around to the front of the booth. Screw one 96-inch stud to the front of the booth, 42 inches from the ground. Place the plywood centered between the two front studs, on top of the horizontal stud. Screw it to the horizontal stud so that half the plywood is inside the booth and half is extended to the outside of the booth. This is the counter top.
Toss the canvas tarp over the entire booth. Square and flush it at the front. Stretch it tight along the sides of the frame. Hammer tent spikes through the pre-made holes at the bottom of the canvas tarp as you would if you were pitching a tent.