Cut a rectangular tray bake into even portions
Mark the rows and columns on two opposite edges before making the first full cut.
Start with how many pieces you want. A 30-by-20-centimeter slab makes twelve 5-by-10-centimeter bars in a grid of six by two, or twelve near-square pieces in a grid of four by three. Sketch the two layouts on paper before you pick up the knife. Think about whether each piece needs to fit a lunch box or leave room for a topping.
If the recipe calls for cooling before slicing, wait for that stage. Lift the slab onto a board using a parchment sling if it has one. Divide each side by the number of pieces along that edge. A four-by-three grid on this slab needs marks every 7.5 centimeters on the long edges and about 6.7 centimeters on the short edges. Mark both opposite edges so you can line up the cuts.
Use a long, clean blade that suits the texture of the bake. Cut along one direction first. Wipe away sticky crumbs between cuts, turn the board and follow the second set of marks. If you trim uneven edges for neat presentation, measure the trimmed slab before laying out the grid.
