I wish to challenge myself to write a 70k word novel. But I can't really decide on the premise that I want to write.
Kingdom building by a god and her disciple?
A post-apocalyptic fantasy where a slave-warrior gains freedom and build a community of freed slaves?
A time travel story where a person wakes up in the future and saw that it has all turn to crap before finding a way to go back?
Can't choose

As the internal dilemma builds, you can add adversaries planning to get the God, the disciple and the slaves back in their hands and you can have them present questions that challenge their perception of the slaves like What are they worth to you?