I ave not heard of this product, but I sure have had fun looking at the link you sent and then look on pinterest and other sites about them---and you're right--everyone just shows finished products and not how pieced together. I'm going to assume based off the products they are selling on the same page you linked, that (to have a perfect fit) you use one of their frames sold separately to lay and cover up the edge of the shaker box. I wonder if the shapes are standard measurements--then you could use your dies. I figure the dimensions given on the product page of the shaker is for the entire shaker--not the part that sticks up from the frame they sell.
Maybe someone else will know....
