Don't use Cavity mill for this.
Planar mill is the answer.
-Select boundary > top face > tool outside
-Select floor (same top face)
-Method = Profile
-Cutting > Stock > Final floor stock = -1.5
Thank you for your solution.
Actually I forgot to mention, that I want to teach that operation to MKE - so boundaries
are bad because they are not compatible. Is there a way to do that?
Another option is to use FloorWall
Now you have to play with floor and wall stock to position the tool correctly
planar mill - better is set floor just bellow the chamfer , tool tip will not collide with wall.
floor wall - set chamfer as a wall, exact positioning, set z-depth offset to get floor preview jsut bellow the chamfer (again, tool shouldnt collide with the wall)
no negative stocks