Cutting a scarf joint
Cut a scarf joint and attach it to the longest wall. First you need two pieces of wall. Join both these pieces tight and later cut the different boards at 45 degrees each. Cut carefully as the scarf joint needs to be screwed. Also, cut scarf’s at both ends. Now use a miter saw and cut the second scarf at a 45 angle. Make sure that both baseboards should fit snugly. Put some glue on it and clean off the excess. Driving one nail towards the scarf will further tighten it and the raised portion of the baseboard will remain solid.
Cutting the corner joint
Cutting the corner joint is also important. First you need to hold the scalp corner and keep it face down. See how long your baseboard is from your wall. Now pick a sharp pencil and try to trace the baseboard profile. It will provide you with a solid reference for further cutting angles.
Cutting outside corners
Carefully cut the outside corners. It will also give you a solid installation of the baseboard. If you have marked pieces earlier, then you can very easily attach both baseboard joints. If you are encountering a doorway and feel that it is a hurdle, cut the outside joints slightly closer to the baseboard. This will allow you to work around the doorway and complete the installation process.
Fill the gaps
Filling the gaps is very important part of installing baseboard coping joints. You can use wood filler and mix with glue. It is crucial that you fill all the gaps of the baseboards. You can also use caulk along with glue to fill the various gaps. Once all of the gaps are properly filled you should have a nice clean finish of the baseboard.