Ideally you will never get actual trapezoidal waveform[with proper edge] out of a BLDC.
As the wiring get better the motor become more FOC from BLDC.
For BLDC motors recommended algorithm is to use Back emf method for sensorless [simple algorithm and circuitry as well] approach. The FOC algorithm can probably make the motor run but wouldn't get any FOC specific features.
Here in this zip you can find example for BackEmf method as well.