Yes what I do, except in Windows 10 without QB64 in PATH and not from COMMAND line and yes you have to save the source in project directory before running writing exe into that same project folder. Valid? It works fine for several years now! The only little snag to this one project one folder idea is making the new folder. I use Windows Explorer but Steve reminds we can make it directly from QB64 with MKDIR (I had to check spelling because I don't use that method because for me it easier to use Explorer and type in a new folder name right where I know I want.)
The only thing I've found (recently) is that QB64.exe has to be in PATH to compile programs in SHELL otherwise you have to be in QB64.exe folder to compile in SHELL (and that is too clunky to do anything little and fast and hidden).
And the question then becomes, "Why would anyone want to that anyway?" ;-)) And if you are just getting over QB4.5 this is not something you need to worry about now, you need to learn all the lovely tools QB64.exe has for you to use.