I’m a Revivalist style Hellenic, so what I’d do isn’t necessarily what other people would do, but I do maintain an altar to our lady Artemis! Creating an altar for a Greek deity is generally a matter of assembling a center focus (such as a statue, candle, plate, etc) which is representative of the deity, then surrounding it with either (or some, or all) offerings or decorations that are pleasing to the deity, a place to put the offerings, or tools and items for use in ritual specific to that deity (such as khernips or blessed water, usually things to cleanse the self or space). It can be quite a freeform exercise. For Artemis specifically, you’d take into account her preferences and priorities: She’s big on nature, and would like ethically sourced herbs and plants; her sacred animals were the bear and the stag, so iconography like antler-shaped candle holders, or a soft false bear pelt as an altar cloth, would be totally appropriate. Here is a wonderful list of offerings to Artemis, and more of her favorites and symbols can be found on her Theoi page.
As for worship, each devotee or polytheist has their own way! If you’re looking to start worshipping or respecting Artemis in a Hellenic Polytheist way, here is a great guide from pomegranateandivy with tons of links on how to get started. If you’re interested in worshipping her in a neo-Wiccan, solitary, or other contexts, you may like to check in with some of her followers.
Personally, my altar to Artemis is on top of a natural wood dresser, with a matching rough natural wood box (that I’ve pentagrammed up… personal practice!), and two silver candle holders in the shape of roots/antlers. There’s also a very small glass jar on the left for tealight candles when I’m doing devotionals or giving offerings (or anything that doesn’t require the whole shebang to be lit). If I have an offering to her that can’t go directly on the wood/dresser, I have a small bowl that I place right in front of the box. I had a much more decorated altar before this one, but for some reason, the minimalism feels pretty good.
Ash