The same question was asked a month or so ago, maybe there's already some answers there that you might want to check out.

My T doesn't have a couch, but I lie down anyways. On a chair too small for that, but I don't mind. On the one hand, I find it helpful to open up. I feel more comfortable like that. On the other hand, my T is not a huge fan of it, mostly because it seems that I can't control my feelings as well as sitting up and I dissociate more.