customise section edges with a curved line

Site URL: http://www.greenshootsandmuddyboots.com/

Im hoping someone could help me create curved sections with some css, i tested the theory of uploading a photo that has been masked with a curved edge, while this works with image blocks it does not work with images filling the background of a section. the site is password protected the password is j4gg3r you can see that I have tried to do this also with cards, place the photo as a circle and this too has not worked. I have watched a tutorial to show how to customise section edges and can see it's possible but how to get the curve?