The frame rest starts life as a 4 1/4" wide piece of material approximately 3/4" thick. The length depends on how many frames you want. You need 6 3/4" per frame. Your first cut is a rip 5/16" off the piece. Now rip another 5/16". Save both of the cutoffs, we'll need them later.
I will write this assuming you do not have a dado blade. For me, it's not worth the effort to set one up for this. If you want to use one, set it up for a 5/8" - 3/4" cut. I use a dado sled.
I just nibble it on my table saw using the crosscut sled. Nibble away 3/4" from the end of the frame rest. Go for about 1/2" depth.
This is how it looks.
Now draw a line on your sled 6 1/8" from the cut line. Draw another line 1/2" from this one.
(Ignor the third line pictured. I tend to scribble on my sled a lot. A scraper makes a good wood eraser.)
Now nibble away the next frame slot. You stop when you reach the second mark. Repeat for each frame slot.
This is what it looks like. After all the frame slots are cut, rip the piece down the center to make two identical pieces.
Now, remember the first pieces we ripped off? Find them. We glue this piece back onto each frame rest. It provides a backstop for the frames and centers them at the same time. You should end up with two frame rests that are about 1 3/4" wide. The glass spacing is fairly critical to limit the amount of burr comb the bees build. If you are using small cell or naturally drawn comb, 1.5" wide would be better. For regular foundation and bees that are not regressed for small cell, 1 3/4" is about right.
