Getting overthrown does takes a lot of time.
There's hints here and there. For example, long missions (I think above 7 days) gives a warning about having some consecuences.
Character descriptions also helps; for example, a very dominant or powerful Slaver, with high respect (usually "feared" or the like) will probably try smething if you're low on respect, or very desired (respect is liked/desired/obssesed with. Each means your own troops actually want to do something to you)
Low supplies and/or low gold makes slavers unhappy, which coupled with being desired and not respected (feared) will most likely end in being overthrown by your most though slaver.
Your aspects also "help". Being a bimbo, a sissy, a slut or any other feature that lower your threath fasten things.
And then, some NPCs will help too, like the 2 right-hand boosts (you can only get one of them, buth both work similarly. One is a rabbit-like girl -I guess intended for male players- and the other is Itzpa'ux the lizardman -intended for female players-)
Overall, the most important feature is being feared or not.Pick as many long-time missions you can (so you'll be out of the camp), and level up a Slaver to be liked-feared. Eventually he'll try (and most likely will) overthrow you.
Good slavers for this are the two uber-NPC golems* (you can find them on Deep Mountain, rare and hard missions), or any NPC you could get as right-hand at the beginning.
Take the bimbo, sissy, oral accomodating, orc cum addicted (or all) aspects at the beginning, wear the sluttiest clothes you can, and try to do the whoring missions.
*one is a shapechanging Golem (also very useful as it has biomancy).
The other is a shemale monster (in almost every sense), that WILL try something unless you're a real badass.