First, table a motion “That there shall be an early parliamentary general election.” You need 434 MPs to back it.
That should be easy if the main opposition has 200+ MPs and has said it won't block an early election.
If in spite of saying it won't block an early election the opposition fails to support one, you then table a "self-no confidence" motion.
That's a motion “That this House has no confidence in Her Majesty’s Government.” You say it's needed because of the opposition's cowardice.
You just need to "win" that motion by 1 vote. It doesn't matter how many MPs back you as long as you "win".
Sounds weird for a government to no-confidence itself as a device to cause an election; but it's happened in Germany.
If you pass your "self-no confidence" motion, you argue that the FTPA allows you to simply wait 14 days. An election automatically follows.
There is a theory that a no-confidenced government ought to resign & let the opposition try to govern. But the FTPA doesn't make that clear.
A sufficiently plausible alternative reading of the FTPA is that the PM could simply sit on her hands for 14 days and force an election.