Cover with boiling water. Bring back to the boil, and boil for 15 to 25 minutes -- until it looks like you can persuade the skins to come off easily.
Remove beets from pot, and let them cool just enough to handle safely. Don't cool them beyond that; the beets should be at least warm going into the jars. The processing time is based on that assumption.
Trim off roots and remaining stem bit, and peel.
Leave very small beets whole; cut large ones into slices, or into 1 cm (1/2 inch) cubes. Cut very wide slides in half.
Pack into half-litre (US pint) jars or 1 litre (US quart) jars.
Leave 3 cm (1 inch) headspace.
Optional: to each smaller jar, add 1/2 teaspoon of salt OR non-bitter, non-clouding salt sub. (Use 1 teaspoon for the larger jars.)
Top up with clean boiling water (such as from a kettle, for instance), maintaining headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Processing pressure: 10 lbs (69 kPa) weighted gauge, 11 lbs (76 kpa) dial gauge (adjust pressure for your altitude when over 300 metres / 1000 feet)
Processing time: half-litre (US pint) jars for 30 minutes OR 1 litre (US quart) jars for 35 minutes.