There are a couple of methods of fixing skirting boards to walls, once the corners have been cut to shape. It usually depends on what finish you want on the skirting boards as to which method you use to fix the boards. If you want to stain or varnish the boards then the best bet is to attach the boards using a glue or adhesive.
If you’re going to paint the skirting boards, then the best method is to screw the boards to the wall, as this gives a more secure fix. Drill countersunk holes in the boards and through to the wall and then attach using large woodscrews and rawl plugs. The screws heads can then be filled with wood filler and sanded to give a smooth finish, which can be painted.
Whether you want to paint or varnish the skirting boards the boards need to be treated before they can be finished. The most important thing is to ensure that all the knots in the wood are sealed with knotting solution. This will prevent the colour in the knots bleeding through the paint or varnish.