How to frame the wall radius

How should I frame frame my wall radius (highlighted area):
1) Should i cut couple of radius shapes ("arches") out of 3/4 ply and glue them together (to get 1 1/2 '') ... somewhat lots of work.
2)Make a "rough" radius using small pieces of 2x1 .. later fill the gaps with putty or exp foam ...
Other ?
Thanks.
1) Should i cut couple of radius shapes ("arches") out of 3/4 ply and glue them together (to get 1 1/2 '') ... somewhat lots of work.
2)Make a "rough" radius using small pieces of 2x1 .. later fill the gaps with putty or exp foam ...
Other ?
Thanks.