My only hesitation about using the almond flour by itself is that I had the experience of making my own gut load and my mealworms started dying. The reason was that the substrate was too fine and they got it stuck in their mouths and noses and suffocated. This may be fine, but if it gets even a little damp, it will clump. As time goes by, the worms eat the substrate and poop in in. Eventually they're living in mostly poop and not so much food. The poop has a different consistency than the substrate. I never used to time it, but when it seemed that the substrate felt different, I'd start using the strainer, sift the substrate into a container to put in the garbage and start the mealworms off in a new bunch of substrate.