Just simply join your connections together, fix to the underside of the base board, then connect to the next board.
Model Rail Electrics - DC/DCC Track dropper connection board - 50 Pack
Model Rail Electrics - DC/DCC Track dropper connection board - 100 Pack
DC/DCC Track dropper connection board - 100 Pack
30 DC/DCC Track dropper connection boards
Model Rail Electrics - DC/DCC Track Dropper Connection Board - 10 Pack