Start from one of the ready-made themes. From there you can set the background colour or gradient, the font, the button shape (rectangular, rounded, transparent), shadows and a frosted-glass effect.
Blocks are reordered by dragging, and changes appear in the preview instantly. Publishing takes one click.
If you want to go further you can add your own CSS. You can also set a custom meta title and description so the page looks right when it is shared.