Hi Roger - cutting into cubes when slightly soft (even fully frozen) and re freezing is what many people do to get control over portion size, some use a big knife, others a pizza wheel - if you have slightly too much, pop it in a mug or similar - cling film over the top and in fridge for next feed - I have found the food is good to go for 48 hours from the fridge.
See - here https://www.youtube.com/watch?v=TGGfwXLdIZY
The other way when fully frozen is to score a line with a Stanley knife and snap - bit like cutting glass.
