Preheat the oven to 350 degrees while you line a 8 x 4 loaf pan with parchment paper.
Combine the boiling water and flax seed in a small bowl; set aside.
Place nuts in a food processor; pulse until finely chopped with a few larger pieces. Transfer to a bowl then set aside.
Heat olive oil in a medium skillet over medium heat then saute the onion, mushrooms, and garlic until softened. Transfer the mixture to the bowl with the nuts.
Stir in the flax seed mixture, tomatoes, oats, flour, sage, parsley, and thyme until well combined. Spoon mixture into lined pan. Bake for 47 to 50 minutes or until loaf is firm and browned. Allow to cool before slicing and enjoy.