Burger/Kraft Slice Style Cheese
Sodium citrate is a salt that is often used in making cheese sauces. When you dissolve it in water before melting the cheese into the same it will prevent the cheese fats and proteins from separating and thus prevents the sauce from becoming grainy. It can also be used to melt, thin, and remold cheese into new slices which have better melting characteristics than the original cheese. 

If I may cite my source (Modernist Cuisine: The Art and Science of Cooking by Nathan Myhrvold, Chris Young and Maxime Bilet, Volume 4, Page 222) and offer a recipe as example: To make 635 grams of cheese slices:


Mix 5g salt, 14g sodium citrate, 6g iota carrageenan, 2g kappa carrageenan and disperse them into 230g of water.
Bring to a simmer
Gradually add 200g swiss cheese and 180g white cheddar to the water mixture, blending with an immersion stick or whisking constantly.
One the cheeses are incorporated continue to blend until smooth.
Pour into a mold and refrigerate for two hours until the cheese sets.


Essentially we just melt the cheese(s) into excess water with some thickening and stabilizing agents. Once it sets slices may be cut off in the case you have a mold. If you don't have the capacity to make nice slices you could pour the mixture directly into a sheet pan so it may set at the desired slice thickness.