Carefully trim the fingers to the right length, allowing seam allowance. Again, too long is better than too short; you can always unpick and redo if needed.

The fourchettes will need to be trimmed to form triangle shapes. The front and back of the gloves are slightly rounded and will meet in at the tip. The red line in the second image shows where to cut the fourchette (fold it in half vertically then cut).

If the gloves you are modifying have a fourchette that runs in one long strip between all the fingers, you may want to use this approach anyway to avoid unpicking the whole length or creating a seam at the tip of the fingers.

Sew the plastic tab to the tip of finger (front or back), and push the plastic bag into the glove a bit so it's less likely to get in the way.

Carefully sew the fourchettes to the front and back of the glove, and sew the tips together. I used whip-stitch with a 3mm (1/8") seam allowance.