Drying Rack: Bartering for It and What It Dries
The 
Drying Rack is not craftable in Eternal Starlight - you barter for it with Stranghouls, the scavenging humanoids of the Starlight dimension. It is their tool, used to dry rotten flesh into the leather their armour is made from, and once you have one it does the same job for you.
Getting one
Trade with a Stranghoul and the drying rack is one of the items on their barter list. It sits in the middle of that list in likelihood, less common than the pungency fruit, seeds and grimstone they hand over readily, but well ahead of the rare items like the 
Seeds Launcher. A few trades will normally produce one.
The same barter pool is worth working for other reasons: 
Deepsilver Nugget in batches of ten to thirty-six, 
Saltpeter Powder, 
Thioquartz Shard, 
Malarite Arrow, and the pungency fruit upgrade 
Smithing Template. If you are farming trades for a rack, none of that is wasted.
Placing it, with or without fire
The rack's behaviour changes depending on what is underneath it, and this is the mechanic to understand:
- Placed over a campfire or other fire, the rack dries quickly and cooks its ingredient.
- Placed on its own with no fire below, it dries slowly, and one recipe only works this way.
What it dries
Five recipes, and the times differ enormously:
Kelp into 
Dried Kelp - 100 ticks, needs fire below
Wet Sponge into 
Sponge - 100 ticks, needs fire below
Clay Ball into 
Brick - 150 ticks, needs fire below
Rotten Flesh into 
Rotten Flesh Jerky - 600 ticks, needs fire below- Rotten Flesh into
Leather - 2,400 ticks, and only without fire below
That last pair is the important one. The same input gives two different outputs depending purely on whether there is fire under the rack. Put the rack over a campfire and rotten flesh becomes Rotten Flesh Jerky, a food described as tastier than raw rotten flesh but harder to chew. Take the fire away and the same rotten flesh becomes Leather instead, at four times the wait.
Why that matters
Rotten flesh into leather with no fuel, no cost and no rarity gate is the rack's real value. Leather is otherwise a cow-farming problem, and rotten flesh is the one thing an overworld or dimension night hands you in unlimited quantity. Two racks - one over a campfire for jerky and bricks, one bare for leather - cover both jobs at once.
The clay recipe is a quiet bonus. Bricks normally cost furnace fuel one at a time; a rack over a campfire turns clay balls into bricks in 150 ticks each and the campfire burns indefinitely.
A simple setup
Put a line of racks on a wall over a single long campfire for the fast recipes, and a second line of racks on plain blocks nearby for leather. Feed rotten flesh to whichever line matches what you are short of, and the same mob drops cover both your food and your bookshelves.
Covers the mod's in-game guide topics: