You need to ensure that only an age verified domestic delivery service is specified - there can be no international shipping nor any options for collection in person, click & collect etc. You also need to check eBay allows the item by checking their knives and bladed items policy.

eBay's AI has been overcomplying with eBay's policy and the Offence Weapons Act ever since the OWA was updated. There have been a few cases where items that didn't even contain a blade were removed by eBay's AI.