Question: how to make fluffy slime that doesn't dry out?
Answer: Add more glue. If you used a recipe that called for glue plus Borax, laundry detergent, contact lens solution, or liquid starch, adding a bit more glue can help the situation. Add a spoonful or so at a time, and knead it in to soften it. Be sure you match the type of glue you add with the glue you made your slime with.