Strategy against two lefties in doubles

Played a doubles team of two left-handers. It was their home field and a very soft clay.

They used the court and lots of slice to take over the net and finish points. My partner and I seemed to be in the wrong spot all day.

The angles they hit were opposite. When we tried to choke them up the middle they hit the low % shot over and over (or what should of been low % to a righty??)

So what special circumstances hold for playing them next time? We want to be ready.