Prepare the Vegetables: In a large bowl, combine the cauliflower, carrots, celery, bell peppers, onions, cucumbers, and garlic.
Dissolve the salt in 4 cups of cold water.
Pour this brine over the vegetables, ensuring they're fully submerged.
Cover and refrigerate for 8-12 hours (or overnight).
Rinse and Drain: After brining, drain and rinse the vegetables thoroughly with cold water to remove excess salt.
Prepare the Pickling Liquid: In a saucepan, combine the water, vinegar, olive oil, oregano, peppercorns, celery seed, and bay leaf. Bring the mixture to a boil, then reduce heat and simmer for 5 minutes.
Pickle the Vegetables: In clean, sterilized jars, pack the rinsed vegetables tightly.
Pour the hot pickling liquid over the vegetables, making sure they are fully submerged. Leave about 1/2 inch of headspace at the top of each jar.
Seal and Store: Seal the jars tightly and let them cool to room temperature.
Once cooled, refrigerate the giardiniera for at least 24-48 hours to allow the flavors to meld. For the best flavor, wait 1-2 weeks before enjoying.