Use an exchange/broker that you can withdraw with lightning from, then withdraw to your own lightning wallet (non-custodial). Then loop out to cold storage when you have enough for a nicely sized utxo. 500k sats minimum, 1mil+ recommended.
If using a wallet like Phoenix be careful, you need to make sure to loop out because they will splice out your liquidity if you send on chain directly.
You can also send back to your exchange/broker (cheaper than loop out) via lightning, and then withdrawal, but this requires you to trust your exchange a bit more not to lock you funds.