Some deck builders install a concrete landing below deck stairs at grade. The minimum size for a stair landing is 36" x 36" in front of the stairs. You will want to rest your stair stringer on 12" of the concrete landing. In this case we are pouring a 4'x4' pad.
Find the location to build your concrete forms. Use a level and a tape measure to determine your elevation. Use the Decks.com Stair Calculator to determine your stair run.
In this case, we used the joist material from the deck tear down for the concrete forms. We used wood stakes to secure the form.
Pour the concrete and level the surface with a magnesium float.