Hi Ether and welcome to the site
My first snake, not very long ago, (only 2 years, so I'm by no means an expert) was a Coastal Carpet hatchling. He was and still is the most placid of all my snakes, and an absolute darling.
He was first housed in a regular critter cage (approx 60cms in length) with a heat mat under one third (connected to a thermostat and timer), a hide cave, water bowl, small branch, and breeder's choice (kitty litter) for substrate.
He moved into a larger enclosure at about 1 year of age, with dimensions of 1200mm H x 800mm W x 650mm D. This enclosure has overhead ceramic heat emitter (connected to a thermostat and timer), two hide caves, one at ground and one at ceiling level, a water bowl, many branches, and breeder's choice over newspaper as substrate.
This is by no means the only way, just what I have used, which seems to have kept my Baby happy.
Here are a couple of pics: