This is the easiest DIY project ever. Have you ever paid what felt like a silly amount for 4 pieces of plastic to lift a bed or a sofa, just to have it be too high and look tacky? I hear ya.
When we purchased our slipcovered couch at the beginning of this year it was a tiny bit long. The slipcover dragged on the floor enough to attract dirt and dog hair... you know, real life stuff.
A little wood glue, and some heavy books to "clamp" the legs together overnight...
Just enough lift to bring the slipcover off the ground -- exactly what I needed. You could easily paint the risers a dark color and help them fade into the shadows even more or use 4x4s if you needed a little more lift.
A 2.5" hole saw is the size used most for putting deadbolts or doorknobs into doors, too -- which is why we happened to have one on hand. So if you don't have one, check with a friend... lots of people have had to monkey with doors in their home.
I love the change it's made -- it's very subtle, but it helps keep the relaxed, lived-in slipcover look from veering into sloppy territory.