Rear wheels are only marginally more time consuming to remove than front wheels. The key is to have as much slack in the chain as possible. You get that by shifting to the small chainring in front, and the small cog in back. Once the QR or axle bolt is loosened (as well as any QR your brakes might have), pull the body of the rear derailleur back (it will pivot back if you put your thumb behind where it bolts to the hanger) and the wheel should drop straight down out of the dropouts. Or you might have to persuade it gently with a smack of your hand on the top of the tire. If you're the persnickity type, and if your bike has a chain hanger on the inside of the drive side seat stay, loop the chain up over it to keep it from flopping around on the chainstay while you're off fixing the flat.