Bricks, Masonry, Asphalt and Concrete - Concrete slab for deck stairs

I would like to pour a slab to support stairs from an existing deck to ground level. At some point I would like to have a sidewalk installed that would match up to this slab. I figure I need to go about 2ft x 5ft x 3ft deep (to get below the frost line). Here's the questions:

1. Whats the best way to build the forms needed? Build the forms first (i.e. plywood box), then dig the hole and install the box, level, and fasten to stakes? Try to build the form in place? Does the form need to go all the way down or just part way?

2. Do I need to install stringer mounting hardware while the concrete is wet or can I drill for fasteners later? It would seem to me that lining things up while everything is wet would be difficult.

3. Do I need to put gravel in the hole first? I know this will help drainage but won't it also allow the slab to settle when the gravel compacts over time?

4. I figure on using bags of ready-mix. Any recommended type?

Thanks for any help.

The landing for the stairs only has to be 4" thick, with a 4" gravel base.
Frank

I figure I need to go about 2ft x 5ft x 3ft deep.

No, you don't want to pour that thick, Frank is right with 4" depth.

Do I need to put gravel in the hole first? I know this will help drainage but won't it also allow the slab to settle when the gravel compacts over time?

Compact the gravel before you pour the concrete.

Thanks for the replies...

I am suprised by the 4" thick. Won't I have heaving problems with frost or is this not an issue because there is very little weight on the slab (sort of like a sidewalk)?

You're right, this is like a sidewalk or driveway, not a house foundation. 4" is plenty.