Salicylic acid sublimes at at 76 °C. This makes it easy to vapor coat a kind of hot bed with salicylic acid. A ball pen like extruder moves then over the thin layer of salicylic acid and dispenses acetic acid/catalyst to form a layer of acetyl-salicylic acid.

We can use solvents as well to dispense solid substances equally on a plane surface. We do that every day, writing notes on a paper, painting...

A simple 'chemical ball pen'. A cleaned ball pen tip (0.5 mm) was glued into the tip of a 2.5 ml syringe with 2-component 5-minutes epoxy resin adhesive. Now we can dispense any chemical on a carrier:

Word 'Hackaday' written on a microscope slide with NaCl crystals. I used saturated NaCl solution with a drop of dish soap to reduce the surface tension of water.