Allie, another potential headache is the grass that grows right next to the outside edge of your box. Even if you put paper down or dig the turf out, ( and those are very good things to do ), that darn grass will creep under and grow up next to the wood, then start spreading out into your soil.
I would use a half moon edger, or a flat nose spade to create a 4" border around your beds. In other words, cut the sod and remove it so you have a dirt frame around the beds. When I edge this way it lasts for about a year before the grass starts creeping back in.
You could also use a weed torch, or a vinegar spray to kill the grass alongside the edge, but in my opinion a 4" border lasts longer and is prettier!