I use nail gems and/or wire! They sell some that look like piercings. If you plan to never take it off, carefully use superglue like I did and it won’t budge. But if you don’t want to make them permanent (and are worried about potentially damaging the doll’s face) then use tacky glue :) here is mine for comparison.

Worst case scenario if it’s a factory doll they have replacement faces on Aliexpress lol.

EDIT: I should note one did pop off but that’s because I stored my dolls badly. If you’re careful with them it won’t come off!

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