To configure a YubiKey's NDEF setting, which controls which OTP slot it will use over NFC, follow the steps below. This is necessary because controlling which slot is used via short or long touch is not possible when connecting via NFC.

Using the YubiKey Personalization Tool

1. Download and install the YubiKey Personalization Tool.
2. Open the Personalization Tool.
3. Insert your YubiKey.
4. Click the Tools tab at the top.
5. Click NDEF Programming.
6. Select the configuration slot you would like the YubiKey to use over NFC.
7. Click the Program button.

Using command-line YubiKey Manager (ykman)

1. Follow the instructions on https://docs.yubico.com/software/yubikey/tools/ykman/Install_ykman.html#download-ykman to install ykman and get it working in your command-line interpreter (Terminal, PowerShell, etc.)
2. Run ykman otp ndef {1|2}, where {1|2} is 1 or 2, depending on which slot you want your YubiKey to use over NFC.

See https://docs.yubico.com/software/yubikey/tools/ykman/OTP_Commands.html#ykman-otp-ndef-options-1-2 for additional details.