Let me start with the concept of materials, also known as "medium" in art circles. This is the actual physical items you use to create your work of
Hence, I suggest using stiffer, yet easy to burn materials, such as cardboard. There are many types of cardboard available at your local grocery store, in all kinds of colours. Since you wish to paint an actual flag, you're adviced to use fine bleached cardboard. The white colour is an excellent background and, unless there's writing on it, completely eliminates the necessity of painting it over with white paint before beginning. This could take half an hour away from your flag production time. If you still end up with coloured cardboard, including the grey cheap cardboard, you have to paint the entire thing white, or the cardboard colour is going to affect the colours you're going to put on it.
Also notice that the Norwegian flag has a 4:3 format, which means that the height is 25% shorter than the width of the flag, which is the same format as a traditional PAL or NTSC TV. You know, the TV you had before your brand new 16:9 Widescreen plasma screen. Cut your piece of cardboard to the correct format. If you can't cut it, remember that it's generally more acceptable that the flag is too wide than too tall.
There are several ways of adding colour to the flag. But seriously, crayons look like a child did it. Nobody is going to believe it is a Norwegian flag, unless it's a kindergarden project. In a demonstration, they are just going to question your intelligence.
Water colours tend to be too transparent, and most oil based paint just take forever to dry. Do you want to burn the flag today or in half a year? Your choice. Personally, I prefer acrylic paint. It has a thickness comparable to oil, yet dry at a speed comparable to water. And I personally feel that it's a lot more managable than your other options.
Masking tape and brushes
You should get some masking tape. It's a lot easier to make the straigh lines when you apply masking tape on your canvas (that's artsy fartsy lingo for "cardboard"), and it comes easily off without destroying the cardboard. You also get away with a larger brush, which makes colouring those large surfaces a breeze.
The height of the flag is 16 units. By unit, I mean one 16th of the heigh of the flag. To get a measurement of a unit in cm or inches, just take the height of your flag and divide by 16. This is from a rule I learned as a child, which is probably why I get so upset when the burning flags are drawn the wrong way. The width of each colour area are 6+1+2+1+6 = 16. On the width, you use the same unit sizes, but then it's 6+1+2+1+12. The 12 is a minimum of the width of the last (top right/bottom right red) colour area. It is supposed to be 12, longer is acceptable, shorter is just stupid.
The blue centre cross
I like to begin with the blue cross in the centre. So start by measuring up 7 (that's past the two first colour fields) units to the right from the top left corner, and similarly to the right from the bottom left corner. Place the masking tape, so that it's right hand side marks this 7 unit line. You also need another strip, where the left side of the masking tape marks the 9 unit line. You now have the vertical line between the 7 and 9 unit lines open, and the sides protected by the masking tape. Paint this area with navy blue. It's a very dark blue. If you make it too dark, it will look black. If you make it too light, like cobolt blue, it will look Swedish.
Take off the masking tape, and feel proud of yourself with the nice straight edges of the vertical blue stripe. When the paint has dried, you can repeat the process for the horizontal blue stripe, which would have the same measurements, except taken from top left and top right corners going down.
Congratulations! You now have a Finnish flag. If you're headed for the Finnish embassy, this is where you stop in the process. And why not? Making a flag is a lot of work, and who cares if it's the Norwegian or Finnish embassy? It's one of those darn Scandinavian countries with reindeer anyway, right?
The red areas
So the stripes in the blue cross are two units wide. The white strips are one unit wide. It's time to fill in the red areas. Since none of the areas actually intersect, you can set up the masking tape for all four corners at the same time. Use this setup to fill the red areas; top right, bottom right and bottom left.
The herring salad
The top left corner is probably the hardest bit. It requires a lot of masking tape being put on and taken off. The internal measurements of the width of the red white and blue stripes are 6+1+2+1+6 like the rest of the flag, and the width of the blue and yellow areas are 6+4+6. It is very important that you include the herring salad in the top left corner, instead of just painting it red. I know it's a pain to put in there, but it's worth the extra effort. The effect on the Norwegian psyche when you include it is precious.
Congratulations. Now, repeat the process on the other side of the cardboard, so that you can see the flag on both sides. Go out, find a journalist, and put your hours worth of work on fire. And don't forget, never let the flag touch the ground, or you will have to burn it! And why would you burn it? Seeing a flag burning on TV is no big deal, but using a flag that indicates Swedish rule over Norway on May 17th is probably the second worst insult you can make to Norwegians. Party on!