Canvases are pretty ambiguous objects, mostly because they're so versatile. Nailing down exactly what they are and how they work is therefore tricky and subjective, but here is the fluff I typically use. Let me know what you think and how you approach this!
To establish a mind-link with a canvas, one first sets their fingers on the canvas. It then draws your desired details from your mind. Using a digital canvas is all about focus: you have to picture exactly what you want and then the canvas brings it to life. You edit by picturing different parts of the image a different way, and the canvas changes accordingly. The canvas has a number of functions that aid with this, including a helpful color palette to aid in color visualization. One can use this palette to use things like paint brushes: the canvas recognizes through the mental link what you expect the paintbrush to do, and reacts accordingly. The canvas is also amorphous and capable of restructuring itself in three dimensions, allowing for 3D models and sculptures to be created, and can also fold in on itself to become a holo-projector or, in the case of a larger canvas, split to become multiple projectors.
When a canvas is set up, it makes dozens if not hundreds of tiny airless spaces in whatever part of it is against a wall or floor, essentially suctioning it to the surface via these vacuums. To reverse this process, one circles a canvas with a solvent device included in handyman toolkits, which begins to reverse this process by filling the vacuums with air and collapsing these little spaces. This is a gradual process, and can take hours or even days in some cases to fully eliminate the bond.
(I will note again, this is just my head canon and not yet ratified! Nothing is set in stone, the canvas has not been set yet.)