Activate Scaled Herbalist by tapping it, putting Arid Archway from your hand onto the battlefield.
When Arid Archway enters the battlefield, it and Elven Raft-Steerer trigger.
Resolve the Arid Archway trigger, returning itself from the battlefield to your hand.
Resolve the Elven Raft-Steerer trigger, untapping Scaled Herbalist.
Repeat.
This clever loop relies on a self-sustaining cycle of land drops and untaps to generate infinite landfall triggers. By using Scaled Herbalist to put Arid Archway directly onto the battlefield from your hand, you trigger Arid Archway's enters-the-battlefield ability to bounce itself right back to your hand. Meanwhile, the constant influx of land entries fuels Elven Raft-Steerer's landfall ability, which untaps Scaled Herbalist each time so you can immediately repeat the process.