Is it possible to use .stl files with Easel?
No. You’d have to generate toolpaths in another cam program.
Got an example of an stl you want to carve?
OpenSCAD (free, multi-platform) will allow one to import an STL file. The projection() feature creates a 2D silhouette based on the z-location of the STL file. For example, a cone shaped STL with z = 0 would create a large circle, while increasing the z value would create progressively smaller circles, presuming large diameter on the bottom. I suspect there are other programs which will perform similar tasks.
What Neil Said. You’ll need another software that can generate toolpaths using .STL files and then you can save the gcode and import that into Easel to send the gcode if you prefer using Easel as the gcode sender, although you can also use any number of other gcode senders as well…
The most common CAM softwares that support .STL are Vcarve Pro, Carveco, & Fusion360.