LEGO® Base Extra Large Building Plate 15 x 15 Platform - Gray

LEGO Dark Stone Gray Baseplate 16 x 16 Mountain with 10 x 10 Hole (53588)

15 Inch x 15 Inch Baseplate for Building Bricks -Two Pack - Green Classic Baseplates Compatible with All Major Brands : Toys & Games

LEGO Medium Stone Gray Baseplate 32 x 48 Raised with Level Front (51542)

Lego Classic : Video Games

Lego Baseplate 15x15

LEGO 628 Base Extra Large Building Plate 15 x 15 Platform - Gray

Light Grey - 15x15 - Used LEGO® Baseplate – Bricks & Minifigs Eugene

What is the largest LEGO base plate you can buy? - Quora

Where can I order thick baseplates like this one? : r/lego