I train in Sambo and love doing heel hooks, leg locks, ankle locks and knee bars from the gurad, YES it is possible!
I wait for him/her to stand on one leg, then open my guard, hook the leg with my foot at the same I shift my body towards the leg. Lift the hooked leg, grab it and I got a BEAUTIFUL ...

Escape from the side mount...

I have two very good Sambo techniques if you want to try them.
1) Place your arm around the persons shoulder and neck, kinda like a head lock.
- your other arm should go under and between
his/her legs, and grab the belt or shorts
above the butt.
- next throw your ...