Kohler Rosario k-3434 one-piece toilet
Flush valve seal replacement

What are, if any, tricks are there to placing a new flush valve seal? There is no hardware. It is a compression seal held in place by three tabs on the bottom of the flush valve. These 3 tabs fit under the porcelain.

Pressing down to fit the tabs under the porcelain with aligning the tabs is just about impossible. Hints, tricks, or encouragement will be appreciated.

Thanks