Slicing buns is time consuming and can lead to inconsistencies in layer halves. Automated horizontal portioning machines slice buns and other bread products into perfectly level layers. The blade(s) and conveyor speeds can be adjusted independently to achieve optimal cut quality, and each Teflon coated reciprocating blade can be raised or lowered to portion the target layer thickness. A top drive conveyor is utilized to hold both the top and bottom pieces in place while the product is sliced, ensuring that each half is level and consistent.