Create Space for the Handles
I cut both holes, and dry fit both handles before proceeding.
Dry Fit of the Back plate 
Simple rectangular cut for the handle hardware 
Dry fit of the handle hardware
We’re now at the point of having a full frame, a back, and holes for the handles on each side. Next is the speaker assembly. This can get a bit tricky, but overall, will be hidden with the speaker mesh, so don’t worry TOO much about appearances at this point.
Build the Speaker Mount
The speaker assembly is two pieces of plywood, joined together with a brace in the middle. The first step is to cut the main two pieces. Although they look similar, the bottom piece is slightly taller, as you can see in the drawing. After cutting the two pieces I sketched out the holes for the speakers. Each speaker hole is 11″ in diameter, and the speakers will mount from behind the hole, not the reverse, as you would assume. The drawings didn’t give specifications for location of the holes, so I simply centered mine with about a 2.5″ gap in between the speakers horizontally.
Next, you have to cut a 2″ wide piece of plywood 26″ in length to brace the two pieces together. You also have to cut this piece at an angle to match the angle of the lean of the top speaker assembly piece. This should be 11 degrees. Once you cut this piece and match up the angle, you can glue and screw it to the two plywood pieces with the speaker holes in it. Use shorter screws here, but make sure you have a tight bond and good contact with all three pieces of wood, as this piece will be somewhat load-bearing in the final assembly.
Finally, add a 3/4″ x 1/2″ frame on the front of the speaker assembly to hold the mesh off of the wood.
Measure and locate where your speaker holes will be with a compass 
Dry fit of the panels before assembly and cuts 
Drill a pilot hole inside your circle, then use a jigsaw to cut the hole 
Jig for maintaining the 11 degree angle needed 
Glued, screwed and clamped to dry at perfect angle 
Back side painted and furring strips added
Paint the Exposed Wood
Now, we have the full frame of our DIY Marshall 1960a, and the speaker brace built. I then spray painted flat black onto the front of the speaker brace, and inside the lip of the cabinet frame. Remember we’ll cover most of this ultimately with Tolex, but painting the whole thing black won’t hurt you, it will just cost you more time and money. I only painted the areas that could possibly be visible after Tolexing. With the dry fit of the speaker panels, you need to make sure there is at least a sixteenth of an inch clearance all the way around to accommodate the speaker mesh thickness.
Spray painted speaker panels. 
Inside of the frame sprayed, just to be safe 
Dry fit of the frame before the speaker mesh goes on
After the paint dried, I laid the speakers on the holes, marked and drilled each hole for the mounting screws. I drilled each hole the same width as the screws I used, so when I pushed them through they were snug, even without a nut on the other side. This is important, as you screws will need to be in place before your mesh.
