Corner blocks and window aprons
Most of the original door and window casings in our old house are mitered, but we have decided to do one room - a later addition that was done with plain flat boards - in the symmetrical kind of moulding that uses corner blocks. So we know how to do the corners, but what we're not sure about is how the window aprons are usually done.
On our original moulding, the apron is simply a piece of the casing placed horizontally, thicker side up so tapering top to bottom, and rounded at the bottom corners. It doesn't seem to me that you could use the symmetrical casing this way at all, even if you did something fancy with more corner blocks.
I would appreciate any help with figuring out what the norm is (or was) for this.