Turn off the water supply to the toilet. Find the valve at the back of the toilet and turn it clockwise. Unscrew the water line and wrap the end in a towel to keep it from spilling water on the floor.
Flush the toilet. Hold the handle down until the tank is nearly empty. Unscrew the floor bolts that hold the toilet in place. Carefully lift the toilet off the wax ring.
Clean the wax ring with a hose. Scrape off as much residue as possible from the floor and base of the toilet. Make sure the bolts that come out of the floor from the flange are still in place.
Install the new flooring and let it cure the appropriate amount of time. Measure the gap between the new floor and the old flange. If it is more than 1/2 inch, you will need to install a closet flange extender.
Install the flexible ring first. Set it in place with a bead of silicone caulking. (If the T-bolts are too short, you may have to replace them before you install the extender.) Set the new extender flange over the flexible ring. Make sure it is close to being flush with the floor. Add another extender ring, if necessary.
Turn the toilet over and install the wax ring in the drain opening, pressing it firmly in place. Set the toilet in place. Thread the bolts extending from the floor into the holes in the base of the toilet. Reattach the toilet with the original gaskets and nuts.