I am not familiar with memory box dies, but I usually stamp first and then cut (even with clear stamps).
If the dies have the reference holes, here is a great video from Taylored Expressions. I do it this way all the time - so easy About Our Dies & Impression Plates
If they don't have the reference holes, here is a tutorial from Barbara Anders. Paper Pursuits: MFT September Teaser, Day One
I use this method, too. You may have to put a shim in your sandwich to get a clean cut with this one depending on your machine and the die.