I used 1/4" red oak I purchased at my local hardware store. It came in boards 6″×48″. So I cut individual parts separately instead of together as the Easel file shows.
After the cutting finished I used a chisel to fine tune the fit for the ramps in the slots to make sure everything went together and was relatively square.
After fine tuning, I sanded all of the pieces and then used a spray poly on each of the ramps, as well as the inside of the tower. During this time I also glued the lower box together.
I glued up the lower box as well as the tower, then used a block plane to round all the corners
On my compound miter saw I cut the top and bottom off the box to make sure each side is perfectly square and flat, as well as make the ramps extend to each end(more visually pleasing, in my opinion)
After sanding and rounding the remaining freshly cut edges I used a spray poly to finish the outside, then sanded it with 2000grit sandpaper and wiped it with some old english.