Looks good to me. The MOSFET will need a heat sink.
How many volts will be across the LED? Probably 3V 3A.
The top of the LED is at 12V. The bottom of the LED is at 9V.
There will be 0.7V across R2. (lets say 1V so the math is easy)
This puts 8V across the MOSFET. 8V x 3A = HOT.
Just for fun lets drive two 10W LEDs in series.
So now there is not 3V but 6V across the LEDs.
The MOSFET voltage will be only 5V.
5V x 3A = HOT but better.
Lets try 3 LEDs.
LED voltage = 9V (more or less, varies with voltage,)
MOSFET voltage will be about 2V.
2V x 3A = 6w Ok that is also hot but better yet.