So off to the fabric store. After several debates back and forth, Adam settled on fabric with flames. I thought it was perfect, very rock 'n roll!
So I simply measured each side of the amp, top, front, and back. I added an inch all the way around; cut out the pieces. I pinned them wrong sides together, turned it inside out and checked the fit. Finally, I turned it back to the pinned edges, sewed 1/4" seem allowance, and finished it with 1/8" hem. Perfect!!