How to achieve freeze dried strawberry flakes?
First off, if they're the texture of raisins, they aren't the sort of freeze-dried strawberries the recipe wants - what it wants is something totally dry, almost the texture of styrofoam. They should crunch if you bite into them, and slowly rehydrate in your mouth if you eat one without crunching. They'll look like full-sized slices of strawberry, only dry. Like this:



The right tool for pulverizing something like this without liquid is a spice grinder or small food processor. If you don't have one of those, put the berries in a plastic bag and crush them with a mallet or a rolling pin.