Making a cheap archery target with Great Stuff foam insulation

**** UPDATE! NEW VIDEO WITH CHEAPER AND BETTER MATERIALS: • Cheapest and Easiest t... ****
This is a video on how to use fairly inexpensive hardware store insulating foam to make an archery target for less than half the cost of most targets found at sporting goods stores.
Some parts of the process are not in the video, so here is the basic way to do this:
Materials needed:
Wood or bricks, layed out to make square or rectangular frame (this is where the foam will be filling in, and will make your target core, which is then sandwiched between cardboard).
3 x Great Stuff Big Gap Filler foam in a black can
Aluminum foil
Cardboard scraps, preferably in the size that your target will be.
Step 1: make your frame out of wood or bricks. Mine is wood in the video
Step 2: lay a sheet of cardboard flat and put the frame on top so that the cardboard prevents the frame from touching any of the ground
Step 3: line the frame with aluminum foil or anything else you have that will prevent the foam from sticking to the frame
Step 4: Spray the foam cans into the area which the framework surrounds, leave a little space between lines of foam, as they will expand a decent amount.
Step 5: After the foam expands and cures, give it time to air out over a few hours time or overnight, then you can remove the frame, and the foil.
Step 6: the front of the target will already have cardboard on it from the sheet you layed down before setting the frame on top, so now you just need to tape another sheet of cardboard on the back and wrap the whole thing with extra tape to hold it together well. If the target seems to warp after removing it from the frame just stand on it or bend it into a flatter shape. It's ok to be a little rough on it!
Finally, all you need to do is set stakes in the ground and find a way to mount the target to them. I just used metal railings and hammered them into some soil in a raised flowerbed area, and slid them between the edges of the target and it's tape.