I think in the best technical way to get through without the agents being able to detect that you have a single satoshi. The most logical would be to memorize the seeds but relying on memory would not leave me 100% at ease. Is there another feasible, safe way?
I think the safest way to go through airport customs with bitcoin is when you have NOTHING with you that can be linked to bitcoin (no seed phrase, no hardware wallets, no pre-installed wallets on laptops and phones).
I'll explain how I imagine it (but this will only work if you've already visited the point of arrival and departure, i.e. the point of arrival is not new).
Point "A" (point of departure): as usual, you create a
BTC-wallet with a secure storage of the seed phrase.
Point "B" (point of arrival): a
BTC-wallet with a secure storage of the seed phrase has been created in advance.
Before the flight from point "A" to point "B" you make a transaction from the 1st wallet to the 2nd and by the time of arrival, your bitcoin will already be in the wallet, and at customs you will not have anything incriminating related to the bitcoin (in case of a detailed inspection).
But this option is not suitable for emergency (unscheduled) flights.