https://www.pcgamer.com/fortnite-duo-ride-shopping-cart-to-spawn-island/

I'm a semi-regular Fortnite player, but I've never once tried to return to Spawn Island. A quick Google search informs me a sizeable chunk of players have made the trip by building bridges, parachuting straight from the Battle Bus, or hitching a ride on a rocket.

Invariably, these methods—the ones I've seen, at least—have fallen short due to the invisible wall that guards the archipelago. As showcased by Fortnite streamer Lachlan, though, it appears doing so while riding a Shopping Cart is possible.