Since you are asking specifically about a custom ROM link for the Oppo A11K, it is important to clarify the current state of this device's development community before providing the review.
SuperiorOS: Known for its deep customization options while remaining lightweight. oppo a11k custom rom link
Enable USB Debugging: Found in Developer Options within your phone settings. General Installation Steps Since you are asking specifically about a custom
Drivers and Tools: A PC with the latest MTK drivers and ADB/Fastboot tools installed. High-Level Installation Guide oppo a11k custom rom link
Unlock Bootloader: Use the MCT MediaTek Bypass Tool to bypass security and unlock the bootloader.