Any creative and force-free ideas on how to deal with this dog training issue?

My young Lab is wolfing down his food. He’s good with food in a bowl, but I have a big bag of kibble in the kitchen. I keep forgetting to close it, and when he gets in there, he eats without chewing. He gasps for at least two minutes after I call him off.

Teaching him not to touch the bag is going well, that’s not the issue. I’m concerned about the way he eats in general. I’m worried that, should he ever have access to food when he’s unsupervised, he’d very quickly hurt himself.

I want to teach him that large amounts of food can be enjoyed slowly. Thoughts?