You can have a ground plane on a 1-layer PCB. It's just a large "pour" that covers all the blank space. Traces are run through channels (the pour just clears any traces). Now you can just jumper to the pour anywhere on the board and have a low impedance ground. Sometimes layout considerations will necessitate wire jumpers to cross over the pour, but it's a small price to pay for decent EM performance.
You'll also save a ton of etchant.