What would I use and how much would I need for the grouting/mortaring per piece?

For a jointing material that will harden, the joints between the “pavers” created with the QUIKRETE® Walk Maker® Building Form can be filled with QUIKRETE® Sand/Topping Mix (No. 1103) or the EarthEssentials by QUIKRETE® Polymeric Jointing Sand #127557. Since the mold will create loose stones to create the individual pattern sections, you will need to form the outsides of the walkway in order to pour in the jointing material. You will need approximately 20 lbs of either of the products mentioned to fill the joints per form.