How to make a "Popcorn Kernel Jar Diversion Safe"

Over at Instructables, attosa has posted instructions for making a lot of cool things, such as a gravity-defying ramen cake, a zombie Snow White cosplay costume, and homemade cleaning putty. She recently made a Popcorn Kernel Jar Diversion Safe. It looks like a plastic jar filled with popcorn kernels, but actually has a hollowed-out space to hide goodies. Brilliantly simple!

She said:

I recently visited a spy shop for the very first time and was very intrigued by their line of secret diversion safes. Most of them were cool but on the pricy side. Some of the objects were rather enticing, making me think they'd be taken if found (I know I'd take some WD-40). Others, like a can of Pringles, I'd probably toss right in the bin. (Goodbye, valuables!) Enter my cheap-as-hell jar of popcorn kernels. Just the right mix of "meh" to be looked over, and nice enough that only a meanie-goat with just throw it away.