nPM1100 is designed to work on a 2-layer board.
Pads D3 and D4 need to be routed to use ship mode. Access to these pads will most likely require a 4-layer board with µvia in the pad. A 2-layer board is possible, but the hole size might set limitations to board thickness. For boards with via in small pads for nPM1100, Nordic recommends the use of via capping to ensure good solderability.