Gifting old iPhones to Family

I am stuck can anyone please advise.

I have a new iPhone and want to gift my old iPhone 6Plus to my mum but, she does not have an apple account so I need to set one up for her.

How can I clear my account and details from my old phone and start afresh setting up a new account on it just for my mum.

I'm not that IT savy so any answers need to be pretty basic to follow.

Thanks in advance to any that can help out.

Martin