The EZ Mount method is the most expensive, but it is quick and easy. However, since you are converting from wood, you can usually get the stamps off the wood blocks with the foam intact. It's actually quicker and considerably less expensive to just coat the existing foam with repositionable glue. Alene's Tack-It-Over-and-Over is a good one; Mono Multi in the white bottle with the green caps is my favorite. It's easier to find, and it's easier for me to control the amount I apply; plus you can use the wide end for spreading the glue.
I started with cling mounted stamps with no images on the backs, so I am used to them that way and it doesn't bother me not to have them. Honestly, though, with sentiments it is nice to have the image on the back, to help with the stamping upside-down problem
You don't need the cling stuff from the fabric store - you just stamp the image on tissue paper and trim it close to the outline, then apply it to the stamp cushion (which is usually still kind of sticky from the block anyway) and coat the whole thing with your repositionable glue. The trick is to try to make sure the tissue paper image doesn't go all the way to the edge of your stamp, so when you put the glue on it seals the edges. That keeps the image from lifting off. (I've tried the cling vinyl and was not happy with it. I didn't think the stamps stuck very well to the blocks at all.)
Once you've applied the glue - and you don't need a thick coating, a thin one is actually better - you just let it dry until it is clear, and then stick the stamps to your arm or your jeans or something where they'll pick up a little lint to help make the glue a little less sticky. Otherwise, the stamps will be hard to remove from the storage sheets later.
Pros and cons: Gluing them doesn't take a terribly long time, and it's much cheaper than the EZ mount. It is a little more messy, though, with the glue sticking to your fingers. Also, while most stamps come off the wood with cushion easily, some of them do not - the rubber will come off the cushion, but the cushion comes off the block in nasty, shreddy, chunks. The glue won't work on those
The EZ mount is more expensive, and you have to cut the stamps out over again, but you don't have them sitting around waiting to dry (and if you're me, accidentally getting one stuck to your elbow and noticing it later). The EZ Mount likes to stick to your scissors when you're cutting the stamps out, but if you have the Tim Holtz Tonic scissors, they're nonstick and that helps. You can also coat the blades with VersaMark ink as you're going along, and that helps.