We did this activity with a group of young men, many of whom had never had a go at sewing before. We included acrylic paints and marker pens to take the pressure off filling the whole piece with only stitching. Some did a small amount of stitching and mostly used paints or pens, others found it relaxing to spend the whole session stitching.
The use of embroidery hoops makes holding the fabric easier and is also a way of displaying a range of very different materials and themes in a uniform way. However this could be done on simple pieces of fabric without the circle. If using the hoop make sure the fabric is well stretched across it and the screws are tight. Leave some of the fabric hanging over the edge so that it can be re-tightened easily before trimming for final display, as the fabric tends to become baggy and loose whilst being worked on.