I had originally done quite a bit of tinkering with tectonics for my world’s map, but found I wasn’t getting the results I was looking for/getting frustrated with just how much was involved to feasibly replicate it.

I found my fantasy solution: while the world was still molten hot from its creation, great elder beasts were plopped down on it, and in their ensuing melee, the mountains, hills, oceans, and trenches were formed. Their now dead forms can still be found on the world, many of the largest mountain ranges, island chains, and deep sea trenches found along their breadth.

I didn’t really answer your question, but you had me thinking of bashing my head against my keyboard for a couple of weeks some time ago!

One possible source of inspiration would be the Zanclean flood, where the Mediterranean suddenly got connected to the Atlantic ocean and filled up quickly. Plate tectonics are cool in that way that they happen very slowly but some of their effects are extremely sudden.

xkcd.com/time is an interesting story about this event

I’ve made many worlds with plate tectonics, it’s my favorite method to make maps!

It’s outlined very well in this book, my favorite worldbuilding book.

It takes some time, especially your first go at it, but I think it’s really fun and adds a lot of realism to the geography.

As someone who isn’t as hardcore about realism, my approach is just to use it as a sort of base to figure out where stuff goes (for example, determining where mountain ranges and resources are), but I don’t bother adhering too strictly to it and if it comes into conflict with another idea I have I’ll usually prioritize whatever that idea is.

For example, I wanted a desert with a mountain range along its eastern and southern sides. So I did it backwards, first drawing the map then figuring out some plausible plates for it and using those to come up with the surrounding areas that I didn’t have plans for.

Though actually I’m not sure if realistically my world should even have plate tectonics, since it takes place on a terraformed moon, and AFAIK smaller planets/moons tend to have less active cores. I probably should research that a bit.