*Note: There is/was a product for this called Stamp-a-ma-jig. If it's out there still...get it:) It's not too expensive and you'll love it.
To make your own 'jig', just use two pieces of wood joined to create a 45 degree angled corner |_ You will also need a nice 4x5 piece of transparent plastic about the same thickness as good cardstock. Your plastic needs enough thickness for your corner square to butt up against it solidly.
1. Place the plastic sheet in the inside corner or your jig. Place your inked stamp in the inside corner and stamp your image on the plastic. You now have a nice image to place on your layout and experiment with positions.
2. Once you have your plastic positioned where you want it. Reposition the jig against the plastic as before. Remove the plastic being careful not to move the jig. Re-ink your stamp and position it where the plastic was previously.
4. If all went well, you should now have your new stamp just where you want it This technique works great when you want to use multiple stamps together to create something new:)
I hope this is helpful!