What does,'I establish mindfulness in front of me' mean?
Ven. Bodhi's translation of AN 3.63:

I collect some grass or leaves that I find there into a pile and then
sit down. Having folded my legs crosswise and straightened my body, I
establish mindfulness in front of me.

Ven. Sujato's translation of AN 3.63:

I gather up some grass or leaves into a pile, and sit down
cross-legged, with my body straight, and establish mindfulness right
there.

Piya Tan's translation of AN 3.63:

There I gather some grass or leaves together into one place and sit
down there cross-legged, keeping mindfulness before me.

Original Pali:

So yadeva tattha honti tiṇāni vā paṇṇāni vā tāni ekajjhaṃ saṅgharitvā
nisīdāmi pallaṅkaṃ ābhujitvā ujuṃ kāyaṃ paṇidhāya parimukhaṃ satiṃ
upaṭṭhapetvā.

Meaning of parimukha from PTS Pali-English dictionary:

Parimukha，（adj．） [pari+mukha] facing，in front； only as nt．adv．°ṁ in
front，before，in phrase parimukhaṁ satiṁ upaṭṭhapeti “set up his memory
in front” （i．e．of the object of thought），to set one’s mindfulness
alert Vin．I，24； D．II，291； M．I，56，421； S．I，170； A．III，92； It．80；
Ps．I，176 （expld）； Pug．68； DA．I，210．

I would say this means &quot;establish mindfulness at the foreground of my mind&quot; or &quot;establish mindfulness as my main focus or main activity&quot;.