You can certainly put a butter board together ahead of time. The butter itself can be spread on the board and stored covered in the refrigerator long before it needs to be served.  Be thoughtful about how long the toppings on the board will last when making it early. Some ingredients might wilt, brown, or leave behind color on the butter. It’s best to put those items on right before serving. Take your butter board out of the refrigerator about 30-45 minutes so that the butter will be spreadable.