You can adjust he measurements for your amp. I would imagine, given how strong this thing is, you could scale it up to a 2x12 combo amp without issues.
My amp has a foot print of 14" x 6.5"
I used what scrap I had laying around so it really cost nothing to make but, you could pick up enough 3/4" birch ply for under $10.
Let's get started!
Step 1: The Layout...
I took a framing square and tilted the amp back until I had an angle I liked. In this case it was 2.5" higher at the front edge. I wanted the front of the amp 6" up off the floor at the front as well. So this meant the back would wind up 3.5" from the floor.
Here is the layout on the sides and then the sides cutout.
Step 2: Adding the Back and Bottom
After clamping the sides together and sanding them flush to each other, I then cut the back and bottom to fit between the sides. The back is 8"x12.5" and the bottom is 7.25" x 12.5". I used glue and 18ga. air nails to hold it together.
If you don't have an air nailer, a hammer and 6 penny finish nails will do.
Here is what they look like after this step:
Step 3: Sanding Off the Corners and Cutting the "feet" Profile
Again, I used a 1" forstner bit and a jigsaw to cut them out.
I also rounded the corners and eased all the edges of the stand to avoid splinters.
Step 4: Finished
I had to drill a hole to slip the chord through because it was keeping the amp from sitting back correctly.
Since I kept singing "Bellbottom Blues" the whole time I was building this thing, I think I will cover it with denim. :)