I wrote answer, below, but I need to clarify first - are you looking to use the onboard drivers on the LaserBoard, or are you asking about how to do this for external drivers? The answers will differ greatly.
Here is the response I wrote for how to use flip the the onboard drivers. However, this is very different when you use the external driver breakout ports.
On the included Smoothie firmware, you would edit the config.txt file on the board’s memory card using the Sublime Text editor on your computer.
Starting around line 48, take the step, dir and en pins form beta, and switch them with gamma. Save, safely eject, put the card back into your board while off, then power it up.
beta_step_pin 2.1 # Pin for beta stepper step signal
beta_dir_pin 0.11 # Pin for beta stepper direction
beta_en_pin 0.10 # Pin for beta enable
beta_current 0.6 # Y stepper motor current
beta_max_rate 24000.0 # mm/min
beta_acceleration 2500 # mm/sec²
gamma_step_pin 2.2 # Pin for gamma stepper step signal
gamma_dir_pin 0.20! # Pin for gamma stepper direction
gamma_en_pin 0.19 # Pin for gamma enable
gamma_current 0.6 # Z stepper motor current
gamma_max_rate 24000.0 # mm/min
gamma_acceleration 2500 # mm/sec²
The ! after the dir pin flips the direction - I recommend individually testing your dual Y axes to make sure they each move in the correct direction, and adding/ removing the ! on each
The currents for the onboard motors do not change, however, the first driver will always be mapped to
alpha_current and the fourth will always be