-aoe verbs drop the -e and add -ɯiŋ in the progressive tense.
We will use ta plaoe (to plow), to baoe (to bow), and to endaoe (to endow) as examples.

3rd Person Singular Present Tense: plaoes, baoes, endaoes
Past Tense: plaoed, baoed, endaoed
Progressive Tense: plaoɯiŋ, baoɯiŋ, endaoɯiŋ

Noun forms maintain the -ɯ: plaoɯ (plow), baoɯ (bow)
endaoment (endowment) is the outlier.