Amazon.com: Strictly Briks Classic Big Briks Baseplate 15" x 10.5" Large Building Brick Baseplate 100% Compatible with All Major Brands | Large Pegs for Toddlers | Single Green Flat Bottom Base Plate :
Amazon.com: Celawork Large Baseplates Compatible with DUPLO | 15" x 15" Building Block Base Plates for Large Blocks | Large Pegs for Toddlers | Large Building Plate Set : Toys & Games