As chance would have it, our portable workbench fit perfectly inside our slide tray and our 22″ Blackstone Griddle fits perfectly on top of that. It's not mounted or anything, but just sits on top. This allows me to simply lift and remove the griddle if I need my whole workbench. The tray extends away from the RV plenty to avoid any heat on the RV and we leave it extended until the griddle cools before sliding the tray back in.
How is your Blackstone Griddle mounted on the MORryde slide tray in your basement?