I have one of these which I use when a 4x12 is too big:
https://www.mojotone.com/Cabinets_x/Cabinets_xx/Mojotone-2X12-Internal-Slant-Extension-Cabinet
It gives you the advantage of a slant while having both speakers still perpendicular to each other.
I think I paid $500/shipped, baltic birch ply, my choice of tolex, grill cloth, and Vintage 30s. One caveat: it didn't come with corners, and I think the edges/corners are radiused to .5", so it wasn't easy to find corners that fit. I think I ended up with Marshall corners.
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