Can you use a saw, drill, and staple gun? Then you can build professional acoustic treatment for hundreds of dollars cheaper than buying. Let's get started.
For best all around performance, we will be focusing on a 24x48x4" panel. These are just as effective at all the first reflection points as they are straddled in a corner to treat bass issues. The first thing we will need to source is the insulation The most popular opinion is Owens Corning 703, but there are many other suitable options out there. You need a density of preferably 4lbs per ft, though you could get away with a little less. Roxul Safe and Sound is 2.5lbs per square ft. While a bit less dense, I have had good luck with this material for other studio builds. The second thing you will need are some 1x4 boards for the frame.
Cut the vertical boards to 4ft, and measure and cut the top and bottom boards to form the frame. Make sure your insulation fits, then screw the boards together. For one side of the trap, I personally choose to use the cheapest fabric I can get. Whatever fabric you do use needs to be breathable. If you can stretch the fabric tight and easily breath through it, you can use it. Take one side of the fabric, and staple it down the length of the wood, pulling tight as you go. Cut the fabric cleanly, and this is now your back side.
For the front, use any color you wish, as long as it is also a breathable fabric like the back. Lay the fabric out on a clean floor and place your trap with the insulation in it, on top of that fabric, back side up. wrap the fabric around the sides, and staple. For the top and bottom corners you will have to fold the fabric to get a clean look (this in no way affects performance, just looks).
You should have one completed bass trap after this. As far as hanging, I use eye hooks and loops with drywall anchors to secure mine. You could also use a french cleat system as well.
There you have it. It really is much simpler than you might have imagined, and takes very minimal supplies. Block out an afternoon and build some traps that will help you not only have a great sounding space, but help you achieve better mixes!