Make sure the components are well held in place before soldering. Some soldering station offers clippers that can hold the DIP switch and the PCB; however, you can use a ductype to achieve the same.
While using cardboard to protect the table from solder may look dangerous, solder cools very fast, and the temperature of the soldering gun is much too low to quickly start a fire. It would take deliberate actions to actually cause safety issues with it.