One way..
Select New Project from the top menu. Name it "4 Open Tracks". Add 4 tracks then select Save Project.
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Now you can open that project and it'll have 4 open tracks ready.
When you're ready to record stuff, just open that project and set the tracks up any way you want with routing, FX, plugins, etc. Do your recording then select "Save project as" from the menu and give it the name you want for that project. This will drop it into the same folder as "4 Open Tracks" and show it just below it.
You can leave it there or move it to it's own folder. The next time you want to work on that recorded project, just Open Project and the "4 Open Tracks" will appear with your new recorded project beneath it. Select your newly recorded project to continue working on it, or select "4 Open Tracks" to start a new project to be saved with it's new name later in the same folder.
You can save all these to better folder locations or just leave them all in their current folder. When you begin each day by selecting "Open project" from the menu, Reaper will always open from the last folder you were in, which will probably be the one all of these new items are in, assuming you haven't navigated away from it before your last save.