Originally Posted by HillRider

Assuming a flat rear tire (and most flats are in the rear; Murphy's Law.) I hold the bike with the wheel off the ground, open the qr flag and hold the rear derailleur back so the wheel just falls out. Then I lay the bike down on it's left (non-drive side) while I replace the tube. I stand the bike back up, hold the rd out of the way and insert the repaired wheel and close the qr.

A front flat is even easier since the bike can stand on it's fork dropouts after the wheel is removed. I do like to lean it against something as the bike isn't that steady just on it's fork tips.