Here are the full instructions for how I do fluffy rice in the oven.
2kg* long-grain white rice (I like Basmati, but other long-grain rice is fine)
60ml oil or 60g butter, melted (optional)
1Tbsp salt (optional) + any other seasonings you like**
3.5l boiling water, stock, or whatever you like to cook rice in**
Put the rice, fat, and seasonings into a full-size 4 or 6 inch deep hotel pan or similar. Give it a bit of a stir to distribute everything. Add the boiling water and cover tightly with foil (or cover with foil and put the lid on, if you have a lid). Bake 40 minutes at 350F/180C, then uncover, fluff and serve. Makes ~40 meal portions or ~60+ feast portions.
*To halve this recipe, use a half-size pan and reduce cooking time to 25-30 min. Don't try to double it-- if you need more, use more pans.
**For saffron rice, put the saffron in a cup of water and bring to the boil. Let it stand 5 minutes, and then combine with enough boiling water to make up 3.5l. One 1g packet of saffron is more than sufficient for 2kg rice.