Add flour, flax, salt, baking powder, herbs and garlic powder [if using] to a large mixing bowl and stir to combine.
Cube cold butter and add to flour mixture.
Using a pastry blender or fork, break up butter pieces throughout flour mixture until butter is spread throughout and mixture is slightly moist [I find that a pastry blender is much more efficient than a fork].
Add milk and stir until dough is mostly combined.
Using hands, knead dough for about 1 minute, adding a little more flour if dough is too sticky (you can knead dough in the large mixing bowl or transfer it to your counter - I do it in the bowl).
Transfer dough to a large floured surface.
Using a rolling pin, roll out dough until it’s about ⅛th - 1/16th inch thick [the thinner the better].
Using a pizza cutter, cut crackers into about 1 inch by 1.5 inches.
Transfer crackers to two parchment paper lined baking sheets.
Using a basting brush, brush olive oil onto each cracker and sprinkle with sea salt.
Put crackers in the oven and bake for 10 mins.
After 10 minutes, swap baking sheets from top rack to bottom rack to ensure even cooking.
Bake for another 8-12 minutes until golden brown.
Remove from oven and let cool. Store in an airtight container for up to one week.
Recipe by Angela Freed at https://www.angelafreed.com/homemade-whole-wheat-flax-crackers/