Hang larger canvases on the wall while it's being worked on. I already do this, and it works better than an easle. For a wall that you don't want to ruin, stretch large canvas drop cloths on the wall and tack them up with upolstery tacks, then hang canvases on top of them so over spray or paint spatter won't get on the wall.
Roy Conn's Studio 1 at Porthmeor artists' stuiods in St Ives
Artists: Chantal Joffe in her studio