Prep and Chop: Start by preparing all the produce into bite-sized pieces suitable for pickling.
Jar Preparation: Allocate 4 pint-sized jars. In each jar, add 1 tablespoon of olive oil, 1/2 garlic clove, 1/2 serrano pepper, 1 bay leaf, 1/2 teaspoon dried oregano, 1/4 teaspoon celery seeds, 1/4 teaspoon fennel seeds, 1/4 teaspoon mustard seeds, 1/8 teaspoon coriander seeds, and a pinch of black peppercorns.
Vegetable Division: Divide the cauliflower, sliced carrots, celery, and red bell pepper between the four jars, filling them to the top.
Brine Creation: In a medium saucepan over high heat, combine the water, vinegar, salt, and sugar. Bring the mixture to a boil, ensuring the salt and sugar dissolve completely.
Pour and Cool: Carefully pour the boiling brine into each jar, covering the vegetables. Allow the jars to cool at room temperature.
Seal and Store: Once cool, cover the jars with lids, give them a gentle shake to distribute the spices, and refrigerate for 36-48 hours before using.