Prepare for fermenting by washing a fermentation vessel with soap and hot running water. Set aside to dry.
Coarsely dice 1 pound of peppers, 1/2 of a yellow onion, and slice 6 garlic cloves. Add all ingredients to the fermentation vessel, along with 1 teaspoon dried dill and 1/2 teaspoon mustard seed.
Combine 2 cups of room-temperature water with 1 tablespoon of sea salt. Stir until completely dissolved. Pour salt brine into the fermentation vessel until the contents are just covered. If you don't have enough brine to cover all ingredients, whip up another batch, 2 cups water to 1 tablespoon salt, and pour until just covered.
Weigh down the ingredients before securing the lid tightly. Set it aside to ferment. Keep your ferment somewhere where you'll see it daily to observe and open the lid and burp it but keep it away from direct sunlight. If you're using an airlock lid or pickle pipe, burping is unnecessary. After a few days, you should start to notice fermenting activity. There will be small bubbles that rush to the top of the jar when you tap it, the jar may hiss slightly when opened, the color of the peppers will dull, the brine will be cloudy, and the brine may leak over the top of the jar and run down the sides. Later on in the process, the fermentation signs will become less obvious, they jar may hiss less or the bubbles may be fewer, but the fermentation process is still moving along!
Allow the sauce to ferment for 7-14 days.
Once satisfied with the level of fermentation, strain the contents of the fermentation vessel and reserve the brine.
Blend the fermented vegetables along with 5 large dill pickles, 1/2 cup of the reserved brine, 1/4 cup white vinegar, and 1 - 1 1/2 cups of dill pickle juice in a high-powered blender or food processor until smooth. I use my Vitamix and it creates a silky sauce. If using xanthan gum, add 1/2 teaspoon of xanthan gum to the hot sauce and blend until completely combined.
Add more brine to increase the salty flavor, more vinegar to increase acidity, or more pickles to increase the dill pickle flavor, or cut the heat, until you reach your desired flavor, feel free to add water to thin down the sauce if required. Optionally, you can run the hot sauce through a fine mesh sieve to make it ultra-smooth. It takes a couple of minutes, but it's worth it.
Transfer the finished spicy dill pickle hot sauce to small jars or bottles for storage in the refrigerator.