Are they not already sticky? The only ones I have that were bought as masks were TH ones, and they came already tacky. I've used them as you describe. I'll find an example. Those ones you linked to, it sounds as if they do have matching dies.
Ok, this isn't the card I was thinking of, but it's one I can find.
SC387 Colour Mask
ETA, this is the one I was trying to find:
MIX 5 Masked