-Dish Washing Liquid
Start with 1 cup of corn starch and 1/2 cup of dish washing liquid, but know that you'll definitely have to add more throughout the mixing.
After mixing those ingredients, we added another 1/2 cup of dish soap, which made it too liquidy, so my scientists told me to add more corn starch. We had a few more rounds of adding more of both ingredients, but ended up with a perfect ball of dough to play with.
After all, isn't mixing and kneading the best part??
I have seen several pins that say this will be quite soupy and stringy, but ours ended up quite similar to play dough with a softer more powdery feel to it. Either way, the kids enjoyed their time making it.