I think it is very different per reader, and that you can find audiences with various mixes.
What is it you wish to write? Do you want to tell a story that contains erotica or do you want the erotica to be the core essence of the writing? If you are doing a very short story, the latter might be easier. Start near the beginning of passion. A scene where they are kissing near the door without full introductions. Then a flashback to them meeting. Then clothing is coming off, then a flashback of growing interest or temptation, denied in the moment. Build the background into small flashes during the warm up to give it room and tease the reader along a little before the big scene.
Or not. Just brainstorming.
