Sit on a stair above him, while he remains standing, so that your head is in line with his crotch. This is a great angle for fellatio and you won’t have the old knee-on-hard-surface problem. Pleasure him until he has to hold onto the railing for support.
Turn around and crawl up the stairs slowly. Sway your hips and lift your bum in the air. Let him take you from behind as you reach up to hold onto the stairs above you.
Crawl up to the very top of the staircase. Turn around, rest your bum on the penultimate step and lie back so that your torso is flat on the landing. Open your legs and do a variation of the Sexy Seagull. Prepare to have your mind blown.
Do you have a staircase in your home? Or will you have to sneak your partner into your offices?