From Longman Dictionary of Contemporary Englishslab of cake/chocolate/meat etcslab of cake/chocolate/meat etcPIECEa large flat piece of cake etc → slab
Examples from the Corpus
slab of cake/chocolate/meat etc• She simply looks satisfied, as if she had just bitten into the most delicious slab of chocolate she ever tasted.• One of the occupied tables contained a man and woman and child, tucking in to great slabs of meat.• Ahead of him a morose-looking man in a cardigan was sorting through slabs of meat in plastic containers. 