With the following calculations, you can choose any value of capacitor in the beginning and then follow the formulas in order to obtain the corresponding components of that capacitor for that boost converter:

Assuming that you want the following configurations:

Input Vi= 12V

Output Vo= 24V

Output Capacitor C= 100 microfarad

Switching Frequency= 25000/s

Output Resistance R= 100 Ohm (I chose this arbitarily and since you are using it in a feedback you can either make your resistance a dynamic resistance or your driver frequency a dynamic frequency)

Since You did not give the switching frequency of your Mosfet, I will assume that the converter is in operation for the minimum value of the inductor and you can choose a little higher inductor than that

D= 1-(Vi/Vo)=1-(12/24)= 0.5

L=[D(1-D)(1-D)(R)]/2f= 250 Micro Farad ( I would choose Inductor value of more than 300 Micro Farad to be safe)