Warning: Spoilers Ahead. - Solutions to the LFC #30
My first attempt. Basic features.
I am still working on the sweep cut solution. hopefully will post before other post the solution. :D
Sometimes we forget that modeling operations like this can continue past the edge of the existing geometry and then loop back at a different location. Similar to the machining operations that would occur on a CNC machine when producing such a part.

3D Sketch and sweep note if you only do a 20 mm you will not remove all of the cube that needs to be deleted.