Make the INSET
The inset is an angled piece attached to the base mainly for decorative purposes. It’s not functionally required but I like the look. You could personalize your panels here by adding an oval, or circles, or a logo, or anything you want.
Just be sure that whatever you use has a bevelled edge so you can remove the panels from the base after casting. A 1×4 (which is actually 3/4 x 3 1/2) can be used to make this. I had some slightly thinner 5/8 inch boards so I used them. Either would work fine.
I rip these at 30 degrees on my table saw and cut to length on the miter saw.
I attach them with glue and screws from underneath. If you don’t use glue then you can change the inset design in future castings.
Make the SIDES
The sides are made from a 2×6. Like the base, they are cut to length on the miter saw.
Then ripped down to width on the table saw. (Depending on the tools you have you might decide to rip just the one side down, and that’s okay.)
After ripping I do the final trim to the exact length back on the miter saw.
The sides are laid out and the hole for the dowels drilled. I use a forstner bit for this but any 5/8″ drill bit would do.
I use a small bench top drill press but you could carefully freehand this or use a drill guide. You want the pipe holder pegs to be at right angles (or 90 degrees) to the sides.
I like to pre-drill the screw holes as well. It makes assembly a bit easier later on.