Open a canvas size 400x400, transparent. Click on tool options/draw and select freehand. Draw a wavy line on the middle of the canvas as shown below. Click on Text, check the selection and antialias and make sure that the text will be centered. See settings below. Delete the wavy line. Click on layers and convert the floating selection to raster layer. Click on flood fill. Floodfill the floating selection with any color you desire. At this point, you may add your text effects and decorations.