I have several larger versions of these floorstanding bass traps already in the 2 channel room. I can't say as if I really need any mre trapping but I'm certainly gonna find out vry soon. Main thing is I needed a project to do and this was good meditation for me as well.
The first units I made I used clear pine and probably spent nearly $200 in 1x8's. This time I tried regualr pine 1x8's and the total was about $35. Big difference in quality though ad even with all the puttying I did, they could hae used more passes.
One box of 2" OC 703 was enough to mke 4 traps 6" thick. With 1x8's you end up with 1.25" left over which I fill in with Foam-by-mail decorative, pseudo-acoustic foam to give it a metro look.

I used 1/8" hardboard strips in rabbit along the back edges to retain the 703 when you push it and the burlap into place.