I made the world's ugliest jig today to align the horseshoe layers, for when I glue them up. Obviously I want them aligned as much as possible, so I took some old scrap from my temporary feet, screwed down some more scrap wood as a frame around the horseshoes (screws coming up from the bottom into the frame siding), and voila, an ugly horseshoe frame. The horseshoes do fit in nice and snug, so this should do the job.
I'm going to use the drill press to drill four mounting holes through the stack of horseshoe layers, and then put 1/8" diameter vertical pegs into the bottom of the jig and stack the layers, with the pegs securing them in place. Then I can glue various layers without worrying about them sliding around when I clamp them.