Build the notched block
The three views below show one part. Build it: start from the full block the views enclose and remove material until your part matches all three. This part's notch does not run the full depth, so the top view is the one that tells you how far back it goes.
The part, in three views
corner 1 of 4
Click a face to cut that block away. Right-click to put a block back. Use Turn left/right to walk around the part: a feature on the far side cannot be reached from here.