*****Use caution when handling sheet metal. It will cut you. *****
When I was a kid an old can was a treasure. They made them a little thicker and did not crinkle them. The cans are not as suitable as they once were but we can still find some metal if we look. Flashing is a good material for a small chassis. A pizza or cookie pan provides a good sized piece of metal. I needed a little chassis for an amp and thought a couple of pictures could be in order. I made an amp a few days ago using a 2" X 4" junction box cover as the face plate. It was a good size so a 4" chassis should be fine. I cut a piece of flashing about 6" X 6". No I didn't measure it was the biggest piece I could get from a piece of scrap.
This is the amp I plan to put on the chassis.
The handy box plate has two mounting holes so all I need are a couple of angle brackets. I made some last week I think will work.