Sitting on the couch cross-legged works for me. The back support is nice.
Over the past few weeks, I've started incorporating standing meditation as well, after reading a book about qigong. It's a much different practice than what most people think when they think meditation — but worth exploring!
I think overall, don't overthink it. There are no hard rules. Practitioners of various traditions will try to say it must be done this way or that, but they are simply lost in dogma.