Clean Slate AX1800 build

Hi i need to build a clean image for the Slate AX1800 guisde i've seen are either out of date or don't work. Please could someone tell me how to do this. I'm looking to build this version

ApNos-d303bd39-devel
OpenWrt 21.02-SNAPSHOT, r16399+159-c67509efd7

Have you tried openwrt website? https://firmware-selector.openwrt.org

If you can't find it there, then you will have to check openwrt forum and see if someone created a customer snapshot for your router. https://forum.openwrt.org