Have some unevenness/depressions in the original wood floor of my house- can I use felt (as described in other posts) to even that out under a floating laminate? Do I staple/tack it down? does it need to be fastened?

The existing flooring is a wood floor, but there is no subfloor. 3/4" thick, 2-1/2" wide, T&G. For a lot of reasons I think I've decided to go with a floating laminate. The house is on pier & beam and has settled unevenly in some areas so the existing floor is not completely level. I don't really want to glue anything to the existing wood if I can help it, because someday someone may want to pop up the laminate and actually try to refinish the floor (maybe even me when i have a better budget).

Thanks again for feedback-

yes, you may. I often use scraps of vinyl, asphalt shingles or other matter that will not compress. Stapling or fastening is only helpful while working on it. Once the floor is installed it will not be moving around.