I use a knife to cut open the package at one end, then close it and slide the bar into a gallon freezer ziplock bag to help it last longer.
You don't need much. Just cut off a small chunk about the size of the LFS bubble pack cubes, and let it thaw in a small dish of tank water. Add it to the tank. Or target feed corals with it. It's pretty easy to use, and fish love it.
If you would like to break up the bar into smaller bags, that would allow you to have the weekly feeding bag while storing the rest in the back of the freezer. I do this with many foods.
When making my recipe, I'll take a large piece of the bar (3" x 3") and use a knife to mince it out finely. This is added to the food processor to stir it into the rest of the prechopped food briefly.