What’s your Fire Giant phase two strategy: arena, roll attacks, mounted vs on-foot?

[Violet.J]

I'm stuck on the Fire Giant in my first playthrough of Elden Ring, and despite being over-leveled with a strength build, his second phase keeps obliterating me. I've watched a few Elden Ring boss guide videos, but they often assume a different playstyle or use late-game gear I don't have yet. For those who have beaten him, what was your strategy for managing the arena and his roll attacks in phase two? Is it better to stay mounted for mobility or fight on foot for better dodges, and are there any specific weapon types or ashes of war that are particularly effective against him that I might have overlooked?