Install Lineage OS on Asus Zenfone Selfie: a slim guide.

Asus Zenfone Selfie (Build Number. ZD551KL)is a budget smart phone priced below INR 12000. The default Android version is Lollipop with Zen UI. Zenfone Selfie can give good performance, if we install custom ROM.  Lineage OS is the leading custom ROM project and it offers official build for Zenfone Selfie. User can install Lineage OS over default Android. Lineage OS can improve the performance of Zenfone Selfie.

Necessary skill set

Basic knowledge on adb and fastboot, TWRP custom recovery installation, flash packages from TWRP. Finally you need the confidence to take the risk of unbrick phone (Void warranty)!!.

[I will not be responsible to what happens to your device while trying following steps.]

Download

Following are the necessary packages to download before the installation process. Copy the downloaded packages to the external storage (SD Card) of your phone:

Marshmallow firmware
Lineage OS
Open GAAps (ARM64) Pico
su (arm64)

Steps to follow
Links along with each step leads to concerned instructions in Lineage OS wiki.

1. Unlock Asus Zenfone Selfie.
2. Install adb and fastboot.
3. Install TWRP custom recovery.
3. Flash the Marshmallow firmware using TWRP recovery [Very important]
4. Install Lineage OS, OpenGAAps and su add-on from TWRP recovery.
5. Restart phone.

Note
How to enter recovery mode of Zenfone Selfie?
Power Off phone.
Long press Power button+Volume down button.

References
https://forum.xda-developers.com/zenfone-2-laser/orig-development/rom-cyanogenmod-13-0-t3317515/page225

http://wiki.lineageos.org/Z00T_info.html#build-guide