Bring the vinegar, sugar, 1 tablespoon salt, the bay leaves, fennel seeds, red pepper flakes and 1 cup water to a boil in a medium saucepan. Add the cauliflower, fennel, red onion, carrots and garlic. Reduce the heat and simmer until the vegetables are crisp-tender, 8 to 10 minutes. Let the vegetables cool in the brine, then refrigerate until chilled. Store in an airtight container in the refrigerator for up to 4 days.