1/2" Plywood, 2" x 2" boards, 1 inch wood screws and some Black and White Poly.
Construct a rectangle out of Plywood. Do this by Cutting Four Identical sides to the rectangle, you must determine the size of these sides depending on height of the plants and how many plants you wish to keep inside. I'll keep this easy. Say we're gonna have a Grow Box that 2.5' length x 2.5' width (square) x 5' high. So you cut four sides that are 2.5' x 5' out of plywood. We are not going to have a bottom to this box it will just lift up to reveal the plants, its easiest, the ground will be the bottom of the box.
After you have your four 2.5' x 5' pieces, cut four pieces of the 2" x 2" to 5' long. We are going to use these in the corners to connect the four Plywood sides together. It's a bitch to screw the plywood together without having these in the corners, it will crack and break.
Now before connecting the plywood sides with the 2" x 2" x 5' pieces, line one side of each of the Plywood pieces with Poly (White side out of course)
Connect all four sides of plywood with the Poly sides all facing inside the box, with the 2" x 2" pieces in the four corners. You should have a 2.5' x 2.5' x 5' box that just requires a top now. Cut a 2.5' x 2.5' square and line one side with poly. Screw that to the top of your box with the poly side on the inside and you now have a enclosure to grow in.
If you wish to have a bottom or require a taller box that can't be lifted up to reveal plants. Cut a 2.5' x 2.5' square just as the top of the box and screw in to the bottom. One side of the box will have to be hinged to be a door.
If you are going to do this I will help you in designing the rest as well. Pretty easy too don't be intimidated.
