Here’s a Facebook video explaining how to make “thick and glossy slime”, for any and all slime-related needs you may have.
The key ingredient is Elmer’s Glue-All [Amazon]; the basic slime recipe is to add baking soda and contact lens solution to “activate” the glue, but that won’t be thick and glossy enough. For that you need school glue, baby oil and generic lotion, added in the precise quantities shows in the video.