We currently don't offer to mount the poster and frame together before shipping to customers. We have chosen to do so to be able to expand our footprint of where we have poster+frames capabilities and be fast and effective in serving your customers.
In our experience end-customers are fine with putting the poster and frame together themselves especially as they typically get the posters and frames quickly with our service thanks to our multiple hubs across the world where we produce and ship framed posters from.