Converting to WordPress

Hi there,
I’m not 100% sure if this is where I should be posting this but I’m new to all of this. I’m a current squarespace user and want to switch over to wordpress.org. Before making the switch I want the transition to be as seamless as possible and would like to draft up a website to switch to. From what I can tell to use wordpress.org I’ll need to use the domain I’m currently using for squarespace. Is there anyway I can use worpress.org to design a website that I can switch over to while keeping my squarespace website active during the designing process?