When making a fused art quilt, fabrics are not joined by sewing them together. To join fabrics, you overlap and iron or fused the fabrics together. The overlap only needs to be about 1/4".
Here's a tip: when joining 2 fabrics, overlap the darker value fabric on top of the lighter value fabric. As you can see above, if the light yellow fabric overlaps the dark purple fabric, a shadow is cast. This looks bad. And I should know having done it many times.