I usually just start in a general direction and see where it takes me.
For instance, maybe I’ll have a handful of scotch bonnets and a couple peaches. Pretty easy pairing. I usually start with some sweated, maybe browned, onion snd garlic. Peaches make me think of nutmeg and cloves so I throw them into the sauté with maybe some ginger. Now I need some acid. Cider vinegar will support the fruitiness, so will wine vinegar but in a different way. If I just want vinegar without a lot of flavor I’ll use rice vinegar. Now citrus. Lime is too assertive in this case, lemon is nice and neutral, orange might work but I don’t want to use more than is needed to support the flavor that I already have going. I don’t want it to taste like oranges. For sugar, molasses or dark brown sugar will go with the sort of tropical feel or maybe I’ll use something lighter if I just want to take the bite out of the acid.
Then it’s just tweaking and straining and adjusting.
There you have it - my stream of consciousness hot sauce recipe. I just pick a flavor, usually based on a particular chile and build on it.