Set-up and move from Squarespace

Hi, I want to move my online magazine from Squarespace to WordPress. I am ok with rebuilding the whole thing, so am not worried about losing content. But I am worried about being offline while rebuilding it. What does the community suggest:
– transferring the domain from Squarespace to a WordPress host and then rebuild?
– build WP site first and the transfer the domain? But then, how do I link my domain to my existing WP site?

Thank you so much for your help!
Nina