I simply use a piece of available paper. I sprinkle my tobacco (usually from a jar) onto the paper, and load my pipe. Then, I fold the paper to dump the remnants and dust back into the jar and seal it up. Then, I put the paper back on my wife’s desk where I got it from.
Since seeing this thread, I’ve been trying to find something around the house that I can repurpose for a tray. I’ve had this scrap of maple butcher block laying around since I built the bar (what it’s sitting on) back in 2003. I may have to dig out the router!
Lucky for me, a buddy in my pipe club makes trays. We're actually working on some custom designs right now - he's laser printing an image on one or two of them for me.
And the Nate King leathet tray is awesome. It's a perfect tray for traveling
Typically, I am in my smoking lounge with a glass table, but when on the fly it's whatever surface is available. If out on the porch, I'll just bring a jar and flip the lid over for a bowl, if necessary.