I wanted a medicine cabinet but most are tiny or overpriced for new.
So, I found a free armoire on CL and resized it. There are lots too choose from with folks getting slim TV monitors, some with fancy wood, sweet connectors and handles.
Resize was done by sawing depth in half , see pics. I drew a surround line and started sawing until it halved. I thought a circular saw would be all that was needed but ended using every saw we had depending on corners or tight areas inside the box. But it wasn't very difficult for the results and turned out great.