"This knife is used to slice meat", "This knife is used for slicing meat" and "This knife is used for cutting meat" should be acceptable.
Why 'memotong' and not 'memotongkan'?
I understand that me-kan is used for verbs with objects.
(This is a repeated post from the same question in the opposite translation direction.)
You don't need to use me-kan in this sentence because if you use me-verb-kan it means you did the activities for someone else. For example: Nana membelikan Dina rumah baru ( Nana bought Dina a new house)