This evolved but underused design is quite simple, in a way, but kind of boggling at the same time.
The essential element here is that the slide must rise from zero (flush with the top of the skirt) to the thickness of the top (15/16”) in the exact distance of the length of the leaf. That’s the basic part.
What’s more interesting is how the two ends interact. That’s not to mention that the slides must be dead solid identical. Frid suggests a fixture for the table saw, and I did as he said (he’s never let me down).
I used glued up 12mm Baltic for the slides. I think they would have had less flex if I’d used something like cherry or maple. But they work fine. I waxed all the surfaces. Fine tuning can be done in the depth of the slots in the end skirt pieces. All that was done by hand with a pull saw and a chisel.
-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"