Since I am reccing; I also rec neuralclone's Five Little Words. This is a very clever way of looking at the time paradoxes in the show and presenting an alternative theory to the construction of Sam. I love the little details which create a whole picture.
Another rec is blancafic's Relic - which, okay, was pretty much written for me and is therefore ten different kinds of cool - and it also features my LoM OTP. But! It's very well written and enjoyable in its own right, with some lovely turns of phrase and general coolness when it comes to the time travel aspect of the show.