Research different styles of Celtic art. Look through historical books, on websites or in magazines to learn to identify Celtic designs. This will help you make Celtic art much more easily because you have a reference point to work from.
Design your picture first, then you will be able to transfer it into a Celtic-style frame. If you are a beginner, copy a simple Celtic knot. This consists of a series of crisscrossing lines, woven in between one another. Practice by drawing a distinctive Celtic shape such as a cross with a circle around the vertex of lines.
Rule a square box on a new piece of paper. Emboss the lines to make a strong frame. Celtic art is contained with such a framework; each piece of design tends to be isolated in a section or panel.
Copy your Celtic design into the box. Use light pencil lines and a ruler to draw straight lines. Celtic art is quite precise and drawing freehand straight lines might ruin the image. Make sure you do not cross the border or frame drawn in step three. Celtic patterns are contained in one panel, without touching the edge.
Finish the design. Check to make sure that if you have used 'S' shapes or spirals, they are repeated within the pattern; this is typical of Celtic art. Incorporate the triskelion (triple spirals) or the svastika which are iconic shapes of the Celts.
Use the black pen liner to go over the top of the pencil lines. Make the frame by using clean lines throughout. Do not smudge the lines. Wait for the pen to dry, and then erase the pencil lines.