The concept of an ergonomic desk can sometimes be mistaken as a sit/stand desk. However, the idea of having an ergonomic desk has much more to do with the set-up of it then the desk itself.
Ensuring you are in a neutral posture and position while seated is the first step. Once comfortable in your chair, the rest of your workstation needs to be set-up to promote maintaining the ergonomically correct posture you’ve achieved in your seat and proper work practices to ensure you don’t inadvertently put yourself into an awkward and/or static posture & position.
For more information on how to adjust your chair, employing proper work practices and setting up your workstation ergonomically, please see:
When looking for an actual desk to help promote a neutral posture and position while seated, it’s most ideal to have a desk that is at the appropriate height, given your stature in a seated position. This relates to your elbow height in a seated position in relation to the desk height, to ensure you are not reaching up to access the items on your desk throughout the day.
Most desks are at a fixed height of between 28”-31” measured from the floor to the top of the work surface. That said, it’s quite common for a person’s elbow height in the seated position to be at 27”, measured from the floor to the bony protrusion of the elbow. What this means is that depending on whether you look at the keys or not (touch typist), the work surface height should be as low as 26”. So it’s important to know what your elbow height is before looking to purchase a desk.
If you’re not sure what you need or how high it needs to be, you can get a desk that can be adjusted in height depending on your needs, without having to pay an arm & a leg to get an electric desk. There are 2 options I suggest looking at that are very reasonably priced and can be adjusted to as low as 23 5/8” and as high as 35 5/8” (for taller individuals). These desks have adjustable legs that you set at the desired height, lock into place and then set-up your workstation accordingly.
The Ikea Thyge desk is less than $100 and is a great option is you don’t need the desk for much more than your computer.
The Ikea Bekant desk comes in a variety of sizes, styles and colors, also very reasonably priced.