I have 2 Tomatoe mated clown fish. A mated pair will host the same anemone and the female is the larger of the two. If they are in good water quality, feel secure in their location and have a flat surface (flat rock) very close by to their host anemone, they may spawn there.
If they are fed regularly, that will help them with the spawn thought.
They will begin to clean the nearby rock or slate that is close to their anemone and one day, may lay orange eggs. Mine clean slate and host the same anemone and look out for one another, but they have not layed eggs yet.
As I have heard, clown fry are difficult to raise, they must have artemia or rotifiers to survive. I am no pro at that because mine have not spawned yet and I don't know if they will, and I certainly need to learn more meanwhile about their care if they do.
That is all I know at this point about whether or not you have a mated pair of Clowns and signs of their pre-spawning behavoir.