Slide-outs work well when the stabilizers are down and the unit is level... That being said - the slide-out will operate without stabilizers just fine (or it should). It is recommended to not put any stabilizers or jacks under the slide out. There are slide out stabilizers (I have a pair) and used them on our last travel trailer when we were setup for an entire summer (they were free)... But I was very careful to adjust them on a regular basis as the main trailer settled down.
Most travel trailers only have crank down/motorized stabilizers (not to be confused with jacks)... they just help stabilize the rocking motion. You could even use the old free-style hand stabilizers. These work as well as any others.