In the past, I've used on ErgoDox with a LapDesk (apparently the LapGear XL Laptop Lap Desk), for my couch computing. I would leave the laptop (MacBook Pro) on the arm of the couch, with the trackpad (or trackball) on top of the closed lid. I would have the monitor attached to an arm, attached to a desk next to the couch, so I could swing the monitor in front of me, and then swing it back when I was done with it. I would put the lapdesk and ErgoDox on the floor next to the couch when I wasn't sitting or needing to use the keyboard.
Is this practical? Mostly -- I used to work from home a couple days a week this way. After COVID, I ended up moving my WFH setup to a different room with a sit-stand desk. But I still have the couch setup for personal computing and gaming. Also, I don't use the ErgoDox at the couch anymore -- that was moved to my office. I use an Atreus62 on my lap, without the lapdesk.
I got a lapdesk many years ago for my ErgoDox usage on the couch.
What kind of lap desk are you using? That'll help where to start. I personally use this: https://www.amazon.com/dp/B07P75NDMB/ref=cm_sw_r_cp_apa_i_rIKMDb1TC55GK
Along with using a wrist support. Keeps it from slipping at all since I wrest it against the wrist pad. https://www.amazon.com/dp/B00006HVNI/ref=cm_sw_r_cp_apa_i_GOKMDbSG11JXH