Bendable plywood, also known as Curve-Ply, Flexply, Wacky Wood and Wiggle wood. Can be purchased at a real lumber store ( not Home Depot or Lowe’s)
Comes in multiple thicknesses, I chose 3/8 and laminated (with wood glue) 2 pieces together to get 3/4
I have pictures and description in my build thread from like 9 years ago. I’ll see if I can link it here.
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