In a blender or food processor, blend spinach with 1 c of warm water. Once liquified, add enough warm water to achieve a total volume of 3 c.
In a stand mixer with a dough hook, combine 2 c flour with the spinach water and yeast. Let sit for 15 minutes until frothy and and a little bubbly. If it doesn’t get any bubbles, your yeast is dead and the dough will not rise.
Once the yeast mixture is frothy, add the oil, honey, and salt. Add 4 c of flour and the vital wheat gluten. Turn the stand mixer on and run until the dough starts to pull away from the sides of the bowl. Using a medium setting on your stand mixer, knead the dough for 7 minutes, adding the additional flour in small amounts until the dough is not longer very sticky, if necessary (test it with clean, dry hands. It might stick a small amount, but wont leave any pieces of dough on your finger).
Cut the dough in half. For each half, stretch so the dough is about the same length as the loaf pan (8 or 9 inches) but twice as wide. Tightly roll it up (like a jelly roll) and place it seam side down in a greased loaf pan. This will help the dough rise evenly and look smooth on top. Cover with a flour sack or other lint free towel and let rise in a warm room for an hour or until doubled in size.
During the last 15 minutes of rising, preheat your oven to 350 degrees F.
After rising, the dough should be peaking over the top of the pan. If your house is a little cool, it might take a little longer. Bake for 30 minutes. Let cool for 10 minutes, then remove from the loaf pans and place on a cooling rack.
If you aren’t going to eat the bread within 2 days, I recommend pre-slicing, wrapping in plastic wrap, and sticking a freezer bag before placing in the freezer. This will help keep it from drying dough and can be frozen for 2 – 3 months.