Old subfloor problem - uneven under cabinets
I am replacing a stove and dishwasher along with counters. The stove is in an island, and the tile floor and hardibacker were butted up against the cabinets, leaving a 1 1/4" drop to the base of the cabinets. Because it would be impossible to remove the stove after counters are in, I want to build up the area with plywood. BUT the subfloor is uneven, both back-to-front and side-to-side. The area is about 20" by 85". I guess I need to level the new plywood, rather than try to shim cabinets and rely on feet of stove - is this right? And should I level using wood shims, or try to use some asphalt shingles? The maximum error is about 1/4".