It will be awkward, but the 14 stitches on the holder will be your thumb. When you cast on the 11 stitches you will need to pull your yarn tight so there is no length of unworked yarn between your existing stitches on needle 2 and the cast on stitches, then work the last stitch of needle 2 and 1st of needle 3 as directed and continue on to decrease gusset of thumb and work palm.
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