foolproof

adj

1. Of a device: protected against, or designed to be proof against, misuse or error.
2. Of an idea or plan: certain to succeed in all eventualities, or claimed to be so; infallible.

   “Dill had hit upon a foolproof plan to make Boo Radley come out at no cost to ourselves (place a trail of lemon drops from the back door to the front yard and he’d follow it, like an ant).”

   “My foolproof recipe is my gâteau fermière.”

   “From Nigella Lawson’s effortless spaghetti with Marmite to Chetna Makan’s foolproof chicken curry – the recipes to turn to when you want easy but tasty suppers”

verb

1. (transitive)To render (something) foolproof.

   “We foolproofed the operations.”