The width of the wall will determine whether or not you need to cut your boards. We needed to cut a couple inches off each one and for that a circular saw was used.
Remember the 2 1×4 boards I mentioned you would need that are the length of the wall. This is the time you would attach them to the wall using the anchor screws. If you are doing a bigger wall, you will need more than just two 1×4 boards. The point of these pieces of wood is to avoid putting too many holes in the wall. Just in case you change your mind in a couple years and want to redo the wall a different way. This way you only need to fill a couple holes, if you don’t use these pieces of wood you would have a bunch of holes to fill.