I would recommend getting there in the late afternoon with enough time left to get it installed, then wait until dusk when they are all in and no longer flying.
I prefer hive staples to hold the bottom board on, rather than straps. The lid can be held with strap, brads, staples, or whatever. Move then after dark, and let them set in the new location overnight, releasing them to fly the next morning. Your seller likely will install the hive staples if you ask.