Since silicon molds are often used to make shaped cookies and candies, each “cube” will take on the shape of whatever the mold is.
You can leave a little air at the top of each depression if you want to avoid the risk of a thin layer altogether.
Use the flat end of a fork or spoon handle to get between the ice and the mold if you are struggling to break the ice loose.
You can use both freezer bags and thinner sandwich bags to make ice.
Leave some air in the bag so that it’s easier to get the ice cubes out after breaking them apart. You only need just enough air that the top of the bag isn’t pressed tightly against the water.
The flattest surface is probably the freezer’s floor, as the grates used to create shelves will let the bag droop and form an uneven block. If you’re worried about spillage, you can put the bag on top of a tray, or inside of another bag.
The longer amount of time is due to the fact that the water has to freeze as a single block, rather than separate, individual pieces.
You should do this while the ice is still in the bag to keep it from spilling out.
Be sure to wash the carton thoroughly beforehand to get rid of any possible food borne illnesses like salmonella.
Make sure there aren’t any gaps by using a square piece and pressing it down into the middle of the dimple to create a seamless lining. It’s a good idea to let the foil stick up a bit above the carton so it’s easier to pull the ice out.
Do this especially carefully if you are using a paper carton, as spray from the water could dissolve the paper.
You can also remove the lid entirely before filling the carton up.
