Have recently started this with DD1 (2y 7m) and am curious as to what others do. DD1 snuggles down on her bedroom floor in what she calls her "white bed" - ie our duvet - and I leave her with a few books and a story tape playing. So far she tends to come out again after about 10 mins, does a wee or gets something, and goes back again, sometimes for another 10 mins or so.
She's not much interested in reading on her own and seems to have lost interest in her story tapes too so gets bored quickly but I'm encouraged by the fact she doesn't come straight out - she certainly loves her "white bed" (she sleeps in a cot at night). Even a 10 min break is good for my sanity and gives me time to settle DD2 (nearly 12m). Am going to carry on with this but am always interested to steal others' ideas if there's anything (other than time) that might make it work a bit better.