This free extension for Inkscape makes it easy to create a solder paste stencil for soldering SMT/SMD components to a PCB.
Commercial PCB stencils are laser cut from steel, but for prototypes it is quicker and cheaper to cut your own stencil on a hobbyist-grade laser. I've found vellum paper (200gsm) works well with solder paste, cuts cleanly, very cheap, can be cleaned with isopropanol (isopropyl) and reused to paste up to 10 PCBs.
This extension ONLY works if your PCB was designed with the open-source KiCad EDA, as it relies on the export SVG feature.
I am amazed how the CAD/CAM community uses Inkscape's capabilities to solve such production problems. I could have used this a decade ago for prototyping/small batch runs. Commercial PCB stencils are extremely expensive for prototyping/small batch runs.