Fiber Trends Children Felt Boot Slippers Pattern CH7. Felt boot slippers styled like a high-top tennis shoe. Children’s X-sm (5″), sm (6″), med (7″), lg (8″). Felt slippers may tend to grow some with wearing, but then so do children. If they become too large, washing will bring them back to size (the slippers, not the children). They are made with Worsted weight wool yarn (130, 160, 200, 240) yards of main color and (60, 80, 100, 120) yards of contrast. Choose a wool that will felt to a firm fabric and always test felt a sample. Finished size is determined by the amount of felting. You may use any yarn that will felt and give you the same gauge.