In a medium bowl, stir together the sweet potato puree, flaxseed, coconut oil, oat milk and yeast. Add the salt and flours and mix well. Tip the contents of the bowl out onto a lightly floured surface and knead the dough, sprinkling with flour as needed, until smooth and only slightly sticky (about 6 minutes). Lightly oil the bowl you were using and place the dough in it, turning to coat. Cover with plastic wrap and leave in a warm place until doubled in volume (about an hour).