SPICE model of coupled inductor
You model a coupled inductor in Spice and other simulators by using a component called "k". "k" needs to be setup (quite simply) by stating which inductors it applies to and, it also needs a coupling factor i.e. by how much the magnetic field of one inductor couples to the other inductor. A negative value for k is the same as the output inductor being wound the opposite way i.e. it produces an inverted output waveform.

So, if one inductor is 1 henry and the other inductor is 10 milli henry (a 100:1 inductance ratio) there is an implied turns ratio of 10:1 when k = 1. If k = 0.5 there is still an implied turns ratio of 10:1. Both the below scenarios produce identical results: -



This is how I set up coupled inductors but there's no reason why you can't split an inductor into its leakage element and its coupled part. But why bother when k does that for you and it looks neater as a schematic symbol.