Preferred method (jar): Place the pomegranate seeds in a tall jar and mash them with a cocktail muddler or potato masher until all the juices have been released. Pour the juice through a fine mesh strainer into a measuring cup or clean jar.
Alternative method (blender): You can use a blender, but it’s harder to pass the juice through the strainer since the skins and seeds are blended into the liquid. Place the pomegranate seeds into a blender and blend until a smooth liquid forms. Transfer to a fine mesh strainer and use a spatula to force the liquid through, so all the skins and seeds are strained out.