Depending on the area you live in, a blunt is rolled in a tobacco leaf or with a special blunt wrap. In the USA for example, a blunt is rolled in tobacco leaves. But one thing that stays the same wherever you go, is that blunts should be rolled pure, without tobacco.
If you use a cigar, take a very sharp knife and cut down the outer part from the top down to 4 cm above the end.
Take out the tobacco and fill it with cannabis.
You can seal the cigar with the strip of a smoking paper or with some resine of cannabis.
Nowadays, you can also buy blunt wraps. These are specially prepared tobacco leaves. Blunt wraps can be used like smoking papers and make rolling an easy thing. They also come in various flavors to enhance the taste.