In reply to Peter H:
without wanting to get into why would anyone want to "go abseiling" discussion - most climbers see it purely as a means to an end, and one to be avoided where possible - if you aren't aware already, the proportion of "climbing" accidents that involve abseiling is surprisingly high.
My order of preferred methods for connecting slings together goes like this : (1)screwgate karabiners (2) two straightgates back-to-back (3) as a last resort, by larksfooting. The larksfoot is a weak knot, but at least it minimises the chance of two loaded slings rubbing across each other too much.
Presumably you were able to regain your start point to retrieve your slings, if so why not just use your (hopefully) low-stretch abseil rope to tie around your anchor? - minimising links in the chain.
these are just my thoughts and understanding of best practice - so are open to question/criticism
Take care