A sortation system and method includes providing a sorter assembly and a slug-building assembly. Product is received by the sorter assembly and sorted to a series of sortation lanes. The slug-building assembly includes a plurality of supply lines supplying product for sorting by the sorter assembly. At least one of the supply lines includes an accumulation conveyor and a slug conveyor. Product is accumulated in slug portions at the accumulation conveyor. Slug portions are combined into product slugs at the slug conveyor. Product slugs are discharged from the slug conveyor for sorting by the sorter assembly.