I want to to build my own boost converter to boost from 12V to 24V and 2A output current
Just to underline what others have said this is impossible, it would require you to break the laws of physics.
Even if you had a 12 V power supply capable of just over four amps, then it would be challenging to design and build a step up converter capable of 24V @ 2A, it is not something you throw together and it works. Search on a distributor’s web site like Mouser and see how much they cost.