I was writing this walkthrough down for my own reference but I realized the whole thing read like a poem and I was quite fond of that. So I'm putting it here.

Spoilers for Outer Wilds (2019) ahead but even if you've played half the game, none of this will make sense to you:

The Ash Twin Ember Project

Kinda like this game's final boss or chapter.

To get to the Ash Twin Ember Project you must go to the Ash Twin.

Then when sand is low enough you will go to the warp tower and stay within the broken tower that represents the Ash Twin of the Ash Twin Towers. (goodness gracious)

I'm sorry, I have to bully the Nomai real quick. When the Nomai were discussing the design for the Sun Station warp, apparently several Nomai had to tell the Sunless City chief, "Erm, technically the Sun doesn't count as a planet."

The Nomai were such dorks and I can believe that they would try to blow up the sun.

Anyways, what you're supposed to do is wait for the sand to sink. Hug the side wall for dear life so the gravity of the Ember Twin doesn't pick you up

and you just gotta get to the warp at just the right time. (This part's tricky)

Once inside, turn off the artificial gravity.

Shut down the Ash Twin Project and guard that warp core with your life dude--

by taking it to the vessel.

The Vessel

Mark it on your map with the ship's computer,

that's all you gotta do.

Follow the indicator,

don't hold your breath

you will need it for later.

And when you activate the Vessel's Warp Drive you will enter the coordinates of the Eye of the Universe

which are:

Just remember: L X N

Put that Ash Twin puppy you brought with you to the Vessel's empty warp drive core and ride that Eye to the great beyond.

Damn you quantum mechanics,

have you and have you not tormented me enough?

When you can't go back, you go forward.

When you can't go forward, you go up.

Bring out that signal scope to meet yourself

they're important.

Click your flashlight on and off until you are presented a campfire

light it

Keep going forward until you meet Esker and then you will the follow the banjo strumming of my husband Riebeck <33

And then you shall follow the poem lines until they make sense

and you will find the oboe of Gabbro.

Find Chert's drum, not that hard.

Then find my ex boyfriend, Feldspar, the way he would've wanted you to.

And my stars, you will find the prettiest bones you've ever seen. Dancing for who? For you, dingo!

Actually they are pointing upwards. Sorry for calling you a "dingo" earlier.

The skeletons will build you a ship but they will be too shy to do it in front of you.

So ride that shuttle to infinity and gather the Nomai helmet.

Solanum, Solanum, Solanum! I've fallen in love with her too.

There is one more if you did it right.

Find the singing song of the one with the broken horn and retrieve their hurdy gurdy.

And tell them of course they can join you.

This is part of the DLC and at this point it's more like a victory lap.

And so,

everyone asks if you are ready

I'm not

I am not I am not I am not.

For someone who was never meant for this world I sure have a hard time leaving it.

But the ending waits for no man

and I have no regrets; except that I ever met the Anglerfish.

and I suppose the credits

deserve to be unskippable

-- Slug