Can I use canned lentils instead of dried?

Oh honey, I wish. Canned lentils are already cooked and way too soft - they'll turn to mush instead of crisping up. Stick with dried lentils (the cheap ones work great) and soak them yourself for that perfect crunch.

Why won't my lentils get crispy?

Two likely culprits: either you didn't pat them dry enough (I'm talking bone-dry here), or you overcrowded the pan. They need space to crisp up properly. Also, check your oven temp - 400°F is the sweet spot.

How do I keep them crispy longer?

The secret's in the storage. Let them cool completely, then stash them in an airtight container (I use mason jars) with the lid sealed tight. No fridge - the moisture will ruin that perfect crunch.

Can I make these oil-free?

You can try, but they won't get nearly as crispy. The oil helps conduct heat evenly and gives that golden crunch. If you must skip it, use parchment paper and bake a bit longer - but expect less crunch. For more on the science of crisping without oil, you might look into air fryer science .