Start with the principle that determines everything else: your first employee gets their own accounts, never yours. Not your email password, not a shared login, not your personal profile with a second device attached. Their own address on your domain, their own seat in each tool, their own entry in the password manager with access granted to specific items rather than to everything. This costs a few dollars a month per person and it is the difference between a normal departure and a scramble to change every credential you own while wondering what was taken.
The actual list is short. An email account on your domain through whichever office suite you already use. A seat in the password manager, with a shared vault holding only what they need. Access to the tools their job requires, granted individually so it can be revoked individually. A payroll platform, which is not optional the moment you have an employee rather than a contractor, because withholding, filings, and new hire reporting are legal obligations with deadlines rather than administrative preferences. And somewhere to communicate that is not your personal phone.
The part that actually determines whether the hire works is written before they arrive, not configured. Take the three or four things they will do most often and write down how you do them, step by step, as you actually do them rather than as you would describe them. This is tedious and it is the whole job. A new person following a written process is productive in days. A new person interrupting you to ask how something works is productive in weeks, and you have effectively hired somebody to reduce your available time, which is the opposite of the intent. If writing a process reveals that it only works because you make judgment calls partway through, that is worth knowing before you delegate it.
Plan the exit while you are setting up the entry, because that is the only moment you will have the full picture. Keep a list of every account they were given access to, and treat it as the offboarding checklist. When somebody leaves, whether in six months or six years, you remove access the same day rather than reconstructing from memory what they could reach. Businesses almost never do this at the start and almost always wish they had.