The possibilities are endless, but it depends mostly on what else you are trying to cram into the plane. I have a pretty full panel. No pictures because the wiring is too messy to be proud of, but I hope my description is helpful.
I used some thicker aluminum sheet to make a simple, flat tray that bolts to the bottom flange of the instrument panel frame and sub panel on the pilot side. The GTR20 is mounted on top with the connectors facing inboard. The GMA245R is mounted on bottom with the connectors facing forward. That position gives me access to the USB jack in the cockpit.
I did something similar on the copilot side, mounting my CO detector on the bottom and GAD29 on the top. The top side of that one also has two risers that hold the GTX 45R tray high enough that the unit can slide out over the canopy rail.