Saw off the board at a 45 degree angle.
If you plan to lever the top edge of the skirting board, carefully tap between the skirting board and the wall with a chisel and hammer.
To protect the wall from dents while you remove the skirting board with the chisel, slide a piece of thin wood between the blade of the chisel and the wall.
Gently tap the side of the skirting board to loosen the nails that are securing the board to the wall.
Remove the nails with pliers.