One way to do this with the only
splay reveal we have is the following.
Draw the thick wall, and insert the
w splayed reveal 10 opening into the wall.
Set the splay angles, opening dimension,
and frame depth you want. Draw another wall
that is set to the thickness of the frame depth
set in the splay reveal parameters,
is as high as the opening, and base elevation
set to the height of the sill of the opening.
Disable both wall ends and draw this wall
in the opening and bring it forward one step.
Now stretch both ends of this wall slightly
so that it's ends just mask the opening's contour lines.
Insert an ordinary window into the thin wall.
Peter Devlin