I activate the starter from my stash in the fridge as directed before baking, but use freshly ground hard red winter whole wheat exclusively for all steps.

2 ½ cups of active starter at room temperature (between 68° and 85° F.)
1 ½ cups of red hard winter whole wheat flour

Mix and let rest for 30 minutes at room temperature.

Add:
1 ½ cups of the same flour as above
1 ½ - 2 teaspoons of salt, depending on preference

I use the quick dough cycle of my bread maker which warms the whole thing up to about 82°, kneads for 20 minutes, lets rise for 10 minutes, stirs, and lets rise for another 5 minutes, but you wouldn’t have to use a breadmaker machine at all. Mixing and kneading by hand or in a stand mixer would work just as well.