Solution was posted by Float in comments, here is a more in-depth guide on how to fix this:

1. Locate the MoreBuilds directory, potentially here:

DRIVE:\SteamLibrary\steamapps\common\ProjectZomboid\steamapps\workshop\content\108600\515555911

OR:

DRIVE:\SteamLibrary\steamapps\workshop\content\108600\515555911

2. Open the "mods" folder, then the "MoreBuilds" folder.

3. Drag the "media" folder into the "42" folder

4. Ensure in game you have the necessary tools to start building.