installing step notch (i need some pointers)

[laid_out_70]

thinking of doing it myself and would love some input and pointers. i plan on using my 110v welder, says it good to 1/4" with flux core so ill just have to do short beads. im assuming it will get hot quick. would like to know the order i would go with instaling which plate first and how to center it over the axle or if i should get a porterbuilt notch tacked together already. i know to use levels and what not.