I am attempting to start the last phase of finishing my basement. All that is left is the bathroom floor. My problem is that there is a clean out and Backwater Access Valve cover that exceeds the floor level by about a quarter of an inch. I would like to lessen the tripping hazard by leveling the floor to as close as those covers.

I was contemplating a 1/4 inch sheet of plywood, cutting out around the clean out and valve cover. If this would work, what type of material should be put under the plywood to fill any unevening gaps so no bubbling affects and/or creeking occurs? The tile would be a roll linoleum material.

What can anyone suggest? Assistance is greatly appreciated.