Got ours December 2019 before the Pandemic. You need the welcome letter and passports and you need to show up in person. This is difficult to do if you are not in HK now due to their long quarantine period. I think they only admit HK residents at this time too.
No appointments needed. Just get a number and wait for your turn. They will send the certificates directly to the US Embassy of your country.
Daddoi got a reaction from Love P in Civil Documents - Police Certificate from Hong Kong