I am trying to book a trip from BWI to BKK, and I would like to stay with OW airlines to retain my BA Gold. OW came up with a good suggestion based on total time, starting with a BA flight to LHR and connecting with a CX flight to HKG. However, when I click on the 'book this' button on the OW website, it takes me to the BA site and BA offers up itineraries with only BA flights. Likewise, if I try to book this on the CX site, I get only CX flights. None of the Kayak-like sites seem to arrive at the OW suggestion.

Is there any way to book the multicarrier flight that OW suggests without calling a travel agent?

I hope this is not a repeat question. I searched this site to find an answer before this posting. Apologies if I am repeating something.