It's heavy, dusty, loud work but if you DIY on the cheap:
-$25 rent concrete saw. Water ones are better but you can wet it down.
-$25 rent jackhammer. The gas one I used was lighter and more effective. Angle grind the bit at 45deg. Use technique.
-Pile concrete and feed into trash slowly, or reuse as walkway edgers or filler later.
-Dig and compact. I'd suggest more than 8" directly around the bolt-attachment area.
-Buy, cut, wire tightly with correct wire, and place rebar. Some can be driven deep vertically. Some should be closer to the attachment points.
-Buy, mix and pour. Harbor Fright has larger mixers or struggle with other.
Calculate this carefully beforehand and have extra. You will need to place strings or marks for where the studs go. Making a template for location would seem most precise.
Threaded inserts for bolts would seem better if the lift is to be removed to leave a flush floor.
There are different types of concrete, varying in strength/density.
Not sure which is correct for this type of application.
There's 5k psi
QUIKRETE® - QUIKRETE® 5000 Concrete Mix and 6k psi
QUIKRETE® - Fiber-Reinforced Deck Mix
(I'm not a pro so get more advice
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