Lay log on side. Use planer to clean up outside surface, working in long sweeps along length of log. Roll log as you go, and overlap each sweep of planer for an even finish.
Stand log on 1 end. Using tape measure and pencil, measure and mark a 3 x 3 square grid on top of log. Corner squares of grid will become legs of your stool – the outer edges will be naturally rounded due to natural curve of log. Other squares in grid are more square shapes, which will be cut away later.
From centre of 1 outer solid square in grid, measure and make a mark 300mm down side of log.
Draw 2 lines connecting mark to nearest corners of stool legs, marking a triangle shape on outer face of log.
From remaining solid squares in grid, repeat steps 4 and 5 to draw triangles down sides of log between other legs.
Wearing ear protection and working from top of log, use chainsaw to make cuts along marked lines. You will need to make 2 cuts on 1 side of log, following triangle-shaped lines, then spin log and connect your cuts on other side of log.
Remove the wedge of waste wood.
Use chainsaw to make cuts along remaining triangle- shaped lines. Remove wedges of waste wood, revealing all 4 rough-cut legs of stool.
Using chainsaw, trim sharp edge off inside corner of each leg, rounding them a little.
Place stool in an outdoor area, free of possible fire danger (such as dry ground matter and overhanging tree branches). Unwind your garden hose and position it nearby. Place fire-starter block between legs of stool, then stack kindling on top. Use long-nosed lighter to light fire-starter.
Use long crow bar to carefully turn log so fire burns evenly, especially if gentle breeze is present.
Once inside of stool legs are blackened by flames (after about 30–45 minutes), extinguish fire with water from hose.
Under running water, use an extra length of kindling or metal scraper to remove loose charcoal matter. Leave stool in shady spot to cool and dry thoroughly.
Flip stool right way up. From ground level, measure and mark stool to 535mm or your desired finished height. Flip stool on its side, then use chainsaw to cut stool to desired height.
Use power sander to smooth sides and top of stool. Brush away dust.
In a well-ventilated spot, spray burnt section of stool with exterior timber sealer. Stand stool right way up, then coat sides and top. Let dry. Apply 2–3 coats of sealer.