Linseed oil can be an attractive natural finish for your woodworking projects. Linseed oil originates from flax seeds and is mechanically oxidated to speed the drying process, resulting in what's called boiled linseed oil. Linseed oil is a very flexible finish that can expand and contract with the wood, but does not offer much protection against UV rays, large water spills, and can allow mildew to grow, so it's best used as an indoor finish. You can easily apply linseed oil using just a few items found at home.
Prepare the surface of your project. Starting with 180-grit paper, sand your project thoroughly until you reach 320-grit. The linseed oil will bring out any small scratches or dents in the project, so they will all need to be removed.
Remove the dust from the project. Blow the dust from your project and wipe it off with a dry rag, making sure the project is completely dust-free.
Apply the linseed oil with a brush or rag. Starting from the inside of your project and working out, rub the linseed oil on the project in the direction of the wood grain (natural lines in the wood). You can apply the oil liberally, as you should not have to rub very hard to work it into the wood. Let the oil soak into the wood for 15-20 minutes and then wipe off the excess with a rag. If you don't remove the excess, it could cause the surface to become sticky and uneven. Allow the first coat to dry at least 24 hours.
Rub the project with 0000 steel wool. This will smooth out any grain that was raised during the application process.
Apply additional coats of oil. Apply additional coats (making sure to wipe off the excess oil after each coat) after allowing each coat to dry for 24 hours and then sanding it with steel wool. The project should feel almost as smooth as glass, if finished correctly. Apply a minimum of three coats and allow a month or two for drying, before the project gets heavy use.
Apply the oil in a well-ventilated area.
Make sure that you keep your used linseed rags in a fire-safe place. As they dry, these rags create heat, and can catch on fire.