Alex Horley-Orlandelli is a prolific fantasy/horror and comic artist who has contributed 40+ pieces of Magic card art since Apocalypse. You can see his work on such cards as Quicksilver Dagger, Cephalid Vandal, Decree of Savagery, Nantuko Vigilante, Grafted Wargear, and Myr Incubator, among many others.
The first step of the creation of a card's art is its art description. The art description tells the artist what the card will do, what its flavor is, and what the mood of the illustration should be. Here were the instructions given to Alex for Orochi Hatchery (called "Orochi Incubator" during playtest):
Location: Snakefolk village
Action: Show a large, vaguely egg-shaped structure in which the orochi (snakefolk) incubate their young.
Focus: On the egg incubator
Next the artist submits one or more sketches with his vision of the art description.
Here's the initial sketch submitted for "Orochi Incubator":
The art team wanted the egg-structure to have an indication of an openable aperture or "escape hatch" at the top of the pod. The art team also wanted the scale of the egg-pod to be represented, perhaps by showing a small orochi figure next to it. Here's Alex's second sketch representing these changes.
With that change made, Alex was ready to expand the sketches into a full Magic-scale canvas and add color for the final art. Here's the finished piece.
And here's how you can see the card in its final state, in booster packs of Champions of Kamigawa.