I'm building an "L" shaped staircase for a 10' high deck. A 6'X6' pad was already poured to support the bottom of the lower set of stairs. Can another pad be poured for the stair landing or are piers required for landings? The landing will be 4'X4'. We're building on a slope and locating piers can be quite difficult.

There are a few methods that can be used to support stair landings and your choice will be effected by the type and slope of the soil at that location, the seasonal weather conditions/concerns in your area, your preference for the aesthetics of a concrete slab or posts with footings and the local building code(s) where you live. I've built decks with stairs that require a landing and cantilevered the landing support from the deck load-bearing structure. You might even look into alternative materials for the structural needs of your project (ie. Iron posts, glue-lam header/joists, etc.).