A desk tray that does not become another pile
A tray works when it has a defined job and an easy route for items to leave it.

Give the tray one sentence
Before choosing a desk tray, describe what it will hold: papers to deal with this week, daily writing tools, or objects carried out of pockets. If the answer is everything on the desk, the tray is likely to become a smaller version of the same pile.
Separate paper from objects that can spill, mark or hide it. A tray for keys and coins has different needs from one for documents. The right depth also differs. A low tray makes a few tools visible; a deep box can conceal them beneath larger objects.
Measure the working area left over
Place a paper outline of the tray on the desk and sit down to work. Check space for the keyboard, notebook and the movement of your arms. A tray that fits the tabletop may still occupy the only comfortable writing area.
If it sits under a monitor shelf, measure the usable height including the contents. A stack of papers can catch on the shelf above and become difficult to retrieve. Leave room to grasp the group rather than pinching individual sheets from a tight opening.
An action tray needs a regular moment when papers are handled, filed or discarded appropriately. It is not a permanent filing system. Keep sensitive documents in suitable secure storage rather than leaving them visible on an open desk just because they fit the tray.
For stationery, choose compartments around the tools you actually use. A long pen and a small eraser need different spaces; dozens of identical squares may not help. Keep a little flexibility for a temporary item instead of creating a perfect layout that fails as soon as a new cable arrives.
Review the bottom layer
After a week, remove everything and look at what has not moved. Those items may belong elsewhere. If the same unused objects keep returning, narrow the tray's job or reduce its size.
A simple washable or wipeable surface can be easier to maintain than a lined organiser with many seams. Follow the material's care instructions and avoid letting cups or damp objects share a paper tray. The useful purchase is a small boundary around a clear task, not an invitation to keep more things on the desk.