Take your cup or bowl, your spoon, and the borax and jelly. You'll want the solution to consist of no more than 5% borax. So the easiest way is to take ten spoonfuls of jelly and put them in the cup/bowl. Then, you'll want half a spoonful of borax. This recipe can be extended to twenty spoonfuls jelly and one of borax, if you need that much.
Now mix it in really well! You have to be deceitful - it's poison, after all!