Best place to sell a gravel bike

Dare I say it here, but Bike Radar's classifieds is the best place to buy and sell.

I've always done well with eBay - sold three bikes and a Di2 groupset that way with no issues and good prices. Just make sure you wait for one of their 1% seller fees offers. Good photos always, ideally plenty of them - you can always link to external hosting if you've got more than 12. Document everything, particularly damage.

If selling for local collection make sure you specify cash only as you can't get eBay/Paypal seller protection on cash transactions. Above doesn't apply if you're posting it via tracked courier but I'd always prefer cash as its lower risk.

Be wary of scammers coming to see a bike and then backing out - this is a good way for a thief to scout out your shed, particularly if you get into talking about bikes. Limit your "reason for selling" to "new bike" or "no longer using" rather than "Yeah, I've got this new Dogma on the way with eTap and a £3k carbon wheelset"

I've found gumtree works, add 10% to what you think you want and let haggling commence...

I've had success with Gumtree.

Facebook, get it on all the local buy sell pages. Facebook has so updated so you only create one post and you can choose to post to multiple groups.

I've had good results with eBay for various large items including bikes.

fwiw I go with photo's of clean items (particularly of any damage etc), reason why it's up for sale, pointers to tech specs etc and a thorough description that I'd think was honest if I was buying it from someone else.  It's then buyer collects and signs a printed copy of the advert as receipt that the item was in the condition advertised when they collected.

I sold a bike on singletrack world a few years ago. They have an extremely active sales page.

Pinkbike classifieds & Facebook groups.

Otherwise you can bow to the god of ebay and pay your fees.