just go to a hardware store and buy some pressure treated lumber(or reclaimed wood works too) some L shaped brackets and screws or nails.
Youll notice it looks uneven… this wall is just plaster with no beams behind it so nails just slide in, and out. Whoever decided to put a false wall up in front of a solid concrete wall with space in between in this apt was not thinking clearly. There are also a million holes that need to be filled… But now i have a spot for some of my shoes. Wish it could have been by the door, but there’s no room. Yet another point of bad apt layout. This is a working with what you’ve got project… the man of the house did a good job of putting it up for me.