You start to configure when either ATC tell you to or depending on your altitude/distance for the airport.
The optimum is to delay the flaps until :
ATC forcing you to(ie 90 base turn and delaying your intercept).
You are sure to achieve a continuous descent until glide intercept,a B737 just like an Airbus 320 I am sure will have idle thrust on the glide at speed 180(no wind).
So if you are on a 3 deg path to the glide configure from up speed to 180 kts starting about 2 miles from glide intercept.
If you happened to be level
before glide intercept when one 1/2 below start to configure from up to 180 kts.
Hope that helps.
PS remember 10 TW will require at least 1 NM more.