The only way to know for sure is to read your owner’s manual. Every camper is different. I would guess with most camper’s you will want to level then extend your slides. BUT, the Entegra motorhome, for example, has you release the air from the air bag suspension, then extend your slides, THEN level your RV.
I’m sure most answers in that FB group were people just telling you how they do it for their model. But nobody can answer that with certainty for YOUR RV without knowing your model.