See how there's a central stem in the middle? All the florets are attached to this core by their own little stems. Separating them is a simple matter of running your knife between the florets and the stem to cut it out.
Once you've removed the stem, the cauliflower will naturally fall apart into large florets.
You can break these large florets down into smaller, bite-sized florets with your knife. Use the tip of your knife like a wedge to cut away the smaller florets growing off the sides. The big ones can just be cut into quarters. You can also use your fingers to snap apart the florets.
And that's all there is to it! A cauliflower of this size breaks down into 3-4 cups worth of florets, which is plenty for most side dishes serving 4 people. The stems are edible, though very fibrous. If you want to cook them, start steaming or roasting them a little ahead of time to give them a jumpstart on cooking before you add the florets. Is this how you cut cauliflower, or do you have another way?
Related: Recipe Round-Up: Roasted Cauliflower (Images: Emma Christensen for the Kitchn)