Another technique is creating a glass colour/pattern bar which can then be sliced with a diamond saw and either incorporated into a slumped vessel or framed alone as I did for the TAP Gallery group Spirit exhibition.
The pattern bar is made up of strips of glass plus stringers, noodles rods, frits and powders. The results are not always predictable but always a joy to see complete after over 22 hours in the kiln. In designing pattern bars it helps if you can think upside down and in a mirror because what you will use is a cross section or slice of the bar and hopefully side-by-side they are symmetrical.
First, again, are the design and the colours then cutting strips of glass the right length but of varying widths. The strips are laid flat and vertically in the colour combinations you want. The key is that as the glass strips melt to form a slab or bar the glass flows and slides. This means that you can create curves and more interesting effects as wider strips melt and reform around narrower strips and rods. The strips are laid direct onto the primed kiln shelf and a dam wall is built around them to ensure the result is a slab and not a puddle.
After firing the slab is sliced and the bars polished with diamond boards or paper. They are a lot of work but well worth the effort and spectacular to see in a final piece. Below is "Wheels of Life" from the Spirit show.