I'd look for a place that is naturally mist free—you'll find pockets of mist free areas as you explore. If the area is relatively flat and mist free this will also help with hunting rabbits.

Has ground you can cultivate. There are two types of ground Mistlands: the grass/green ground that you can cultivate and then the "stone" ground that you never can.

Has at LEAST 2 nearby Ancient Roots of sap extraction. Ideally 3-4 or more, though.

My "base" in Mistlands is little more than a place for my portal, mushroom farming area and a Smelter to make iron to then make a Blast Furnace I needed to make the Sap Extractors...