The best option might be the find the local empire/kingdom and approach them, offer to become some vassal state. I mean you already got the land cleared, proved your heroism enough that depending on the government they should be fine with knighting you or the like and giving you a title. And free city is free city, extending their borders and their power. And as a vassal to their state they would probably be more than willing to round up some serfs and tell them to go there, do what the Dwarf tells you. And due to allying with a neighbor you get the additional military support from any opportunistic forces that might be out there. Like said Forest Orcs who would love to overrun a now undefended fortress and claim it as their own.

Typical lord of the next land over would probably accept the deal. It's cheaper and easier than starting from scratch. He didn't have to invest in a military campaign to stamp out the local population. In tithe and taxes it fills his coffers much more in the long run than the small start up costs. Only real reason I can see that they'd refuse would be that they are wholly occupied elsewhere, like in a full scale, no holds barred, war with some other border.