I am building a island dining table base (quartz top 36x70"), it's pretty top heavy. but I framed legs with 4x4 and lag bolt/pocket screwed 4x4 as center beam and 2x4 support.
Farmhouse Table Frame Build (Farmhouse Table Series 1 of 5) with Carolina Leg Company table legs - YouTube
Coffee Table Frame made from single Cedar 4x4. Nothing crazy, but pretty jazzed about the cost effectiveness. : r/woodworking
Wooden Rectangular Table Frame
Steel Table Base Industrial Legs Made Metal for Dining/Coffee/Office D – RusticLand
NIANXINN Solid Wood Rectangular Frame Table Legs,Height 45cm Heavy Duty Wooden DIY Furniture Table Legs Coffee Table Legs with Screws for DIY Table Desk Breakfast Bar Stand Bench (82x42cm) : Amazon.co.uk: DIY