You need Board Bag
When I bought my boat several years ago, it came with a board bag. It's constructed out of sunbrella material and has compartments for each board and one draw string opening. It has worked great. It keeps the boards all together and protects the finish on the boards. I usually put the bagged boards in the stern locker or in the quarterberth while aboard. If my next boat dosen't have one...I'm sure I'll get one made. I'm sure that most canvas shop shops could make one for you or you might try making it yourself.