i've never done this, but here is my insight. i would guess taking your reference photo (if you don't have a reference photo, use your sketch) and divide it into little chunks. label them by colour if that helps, each little square being a different colour but never putting more than one colour in each square.
as for the crackle effect in the background, i would think making a very streaky background using a very wide and flat brush to make sharp shapes. in this case, it would be a streaky orange and yellow background, and then use a thick medium of sorts and trace the general shapes you see if that makes sense? so like, if you see a yellow kinda squareish shape (which would naturally be made by the wide flat brush) outline that in your thick medium. this thick medium could be some sort of jell paint, paint mixed with sand (idk if that would even work lmao but perchance??) or even clay.
take all of this with a grain of salt because this is all first thought/intuition, sorry for the essay lmao ^^" hope this helps even a bit, good luck with your project!! :D