LEGO Plate 16 x 16 with Underside Ribs (91405) | Brick Owl - LEGO Marketplace
Amazon.com: Brick Loot 10 Pack Compatible 5 X 5 inches Baseplates 16 x 16 Studs 16x16 - Variety Base Plate Pack Includes: Grey Green Blue and Tan, 100% fits Lego : Toys & Games