Use cup-for-cup instead of white, unbleached all-purpose wheat flour. Apparently ground chia seeds (can grind them in a coffee bean grinder or a powerful blender) can be used in baking instead of flax and I would be inclined to use about 6 tbsp or maybe even 4 tbsp, as they do suggest using less than the flax in recipes. Add ground chia seeds to the WET ingredients. You'd need to do some trial and error with one of my easy muffin recipes to see how it turns out for you. Of these two variations, I believe the Oat flour variation has been the most popular. A girlfriend of mine used that bake mix for years with success. Oat flour and whole wheat pastry flour (different to whole wheat flour) have about the same number of carbs. You will also find this bake mix in my Splendid Low-Carbing For Life, Volume 1 cookbook.
PLEASE NOTE: The oat flour variation is by far the most popular of the two bake mixes. Please scroll down for the recipe!!
*Einkorn flour = ancient wheat without today's problems