The beauty of building your own electric skateboard is CHOICE. Choosing your own deck has to be the single biggest reason people decide to build their own electric skateboard.
You might have an old school Christian Hosoi Hammer Head that you want to use, or you might want to build your own deck from scratch. The point is when building your own eboard you can.... you have the CHOICE.
But not all decks are suitable, here is a summary of things to pay attention to:
Concave - The curvature between the two sides (left-to-right) of the board. Concave helps hold your toe and heel in place, giving the rider more control of the electric skateboard. Concave locks your feet into your eboard deck while carving in and out of turns. When building an electric skateboard on a deck with a lot of concave you want to avoid having a wide component housing, as it won't sit flush beneath the deck. Long & skinny is better.
Camber - The amount of upward bend along the length of a skateboard deck between the two trucks. Because of camber, the riding platform is set higher than the truck mounts. Camber allows the rider to have more leverage for turns while riding the skateboard. On more flexible decks, camber ensures that the rider will sit at the same level with the trucks (rather than below them). Also, camber allows for boards to have a lot of flex without letting the deck touch the ground unexpectedly. Boosted boards made a really nice electric skateboard using a flexible deck with camber so its not impossible, but it just means you need to split the components apart, which adds to the cost of the build and complicates the build. It also lengthens the battery wires which can be a problem for some ESC.
Rocker - The Skateboard deck bends downward in a smooth arc (like a banana) so that the center of the board is below the trucks. Because of this arc, the nose and tail are “wedged”, allowing more turning in the front and rear trucks. Rocker is good for long distance pushing since now the deck is lower to the ground. This is also known to make for a comfortable freeride deck since it decreases the stress on your knees and ankles. These should be avoided as you don't want your expensive electronic stuff grinding across the ground.
“W” Concave - This is the concave that takes the shape of a “W” in your standing platform. The bump created is also referred to as a “dome”. This “dome” fits the arches of your feet giving you more control with your back foot. This can work really good for your eSk8, However the "W" profile will generally mean that the underside of the deck is not flat so mounting can be a problem. You will definitely need to screw or bolt your enclosure onto the deck, double sided tap won't work as the mounting surface is not flat.
Drop Deck - This form of deck involves an effective foot platform that is dropped to sit significantly below the truck level. The main advantage of the drop platform is that it can be lowered to barely clear the surface, although the actual deck height ultimately depends on the size of the wheels. The lower center of gravity creates more stability and causes less stress on the knees and lower back. These decks can work! But you need really slim components or large diameter wheels, probably both.
To learn more, check out this full article I wrote: What deck is best for building your own electric skateboard