Looking to make a four foot handicap cement ramp at the end of the house
walkway. The walkway is about 3 feet wide. There will be about a 5 inch
drop in those four feet. I am going to remove the last 4 feet of level
concrete before I begin.

I was thinking of making a form with 2x4's on the long sides and thinner
plywood at each end. Then, nail a piece of plywood over the top. Pour
cement into the form and let it harden.

Couldn't find much on how to actually make this type of ramp. From what I
read, it didn't say anything about putting a top piece over the form.
Rather, (if I remember correctly) it said to make the mix somewhat firmer
and start pouring at the lower end.

Which way would be better? Or, should I look at this project differently?

Other questions:
Should the flooring be level and just the surface angled? I plan to add
some small stones before pouring.

We live in New England. I bought the cheap $3.00 a bag Quickrete Concrete
mix from Home Depot. Should I have bought the better mix for the colder
weather?