It has been years since I have done any of this stuff, but there are two ways I know of to approach it
1 you can make it using foam in place and shape it how you want to, a little fiberglass and resin to holt it all together and then you bondo it up to the final shape you want.
You then use that pattern to make a mold from but applying formingnthe fiberglass mold on the form you just made. Use the mold to create the actual console you will be using.
Advantages......
The final product has a nice finish to the point that you can us a colored gelcoat and it can me a finished colored part as it comesmout of the mold.
You can use the mold over and over again to make a bunch of them if you wanted
Disadvantages....
You need to be sure you can get it out of the mold, so a less complex shape
More steps in the process
Method 2
shape the foam as you want but be surenyou make it a little undersized. Apply your fiberglass and resin in several coats and be sure to make it as smooth and flat as you can get it.
When everything sets up you can dig out the foam, sand and fill the outer surface and then you have the final product right there.
Advantages.....
This method will allow more complex shapes that the above method where you hace to worry about getting it out of the mold.
This method is quicker
Works good especially if you plan to cover it in foam and upholstery.
Can be done in place like forming a big dash and console in a car where it will remain in place bonded to the car and you just dig the foam out from behind it
Disadvantage...
One shot deal and then you start again
Can be a lot more finish work depending on how it it shaped and how good at fiberglassing you are
It may be hard to judge how undersized you need to make it