When to apply for EAD

[Emma Tempest]

Hi I have an L2 visa and am planning on moving into the US next month with my partner who has an L1 visa. When is the earliest I can apply for EAD? It is my understanding that it can take up to 3-4 months to process so I would like to start ASAP. Can I apply for it whilst still living in the UK? Do I need to have an address in the US or physically be there? I can't find this information anywhere.

Thanks in advance!