(If you already know all about wine/prefixes, just skip to the end, that last codebox is what you’re looking for.)
I (not so) recently switched to almost exclusively using Ubuntu, even for gaming. There are a few games that I play that still require windows, but not many. On the off chance that I feel like playing one, I don’t always want to load up the sluggish, pester-prone windows. The solution is of course, WINE (which stands for WINE Is Not an Emulator). WINE is a compatibility layer that will allow Windows executables to run on the Linux kernel. It also has implementations of many key Windows features, including the ability to translate Direct3D into OpenGL. A prefix is sort of a little bottle, because WINE isn’t perfect, it often requires workarounds to get some software to run, and the workarounds just aren’t compatible with each other sometimes, so you need the ability to separate them. Winetricks is a piece of software that performs common workarounds with a simple interface. You can create a prefix anywhere with the following command
WINEPREFIX='/path/to/folder/' wine 'wineboot'
The folder should not exist yet when you run that command, as it needs to create the folder itself. I found that when I did this though, winetricks didn’t know about the new prefix! So I had a problem… Being a particularly advanced user I knew plenty of ways to make that work from the command line, but that’s no fun. So I decided to poke around a bit, and I found the directory where winetricks creates prefixes when you use it to install one of its default apps. If you create a wineprefix in this directory, you will find it in your winetricks gui! And that directory is: