Those photos show 23/32" (3/4") shop grade Birch/Maple. The same thing could be built with 15/32" also called 12 mm Birch multi ply.
All the straight cuts were cut with a table saw or chop saw. After all the straight cuts are made then the curvatures were laid out with what ever shapes were convenient to me. I use a french curve with station marks so I can replicate similar curves on multiple pieces.