We use Osmo oil.
Your fitter should get on about 4 or 5 coats once it’s installed and then if you carry on oiling it you’ll keep it nicely moisturised and water resistant.
I’d do a month later, then 3 months then 6 months and then once a year. Or whenever it’s looking dry.
Last thing at night is best. Just take everything off and rub it over with a lint free cloth. By the morning it’s ready to go.
Pay special attention around the sink as that is the most vulnerable.
Hope that helps!

Yes, very helpful. It’s really beautiful. Thank you!

No problem. And yes it is American black walnut