[glend (Glen)]

I hand dug my pier footing on a sloping block, and hand mixed the concrete for a wet on wet pour - and I'm 65 so it can be done. Saying that it took me two days to dig the pier footing hole in mixed conglomerate sand, rock, clay to get down to the pure clay below. My footing finished up smaller than your one cubic metre @ 750 x 750 and 750mm deep as I was never going to put anything heavier than my NEQ6 head and 10" imaging newt on top. To ensure lock deeper in the ground I also drove galvanised steel angle into the clay at angles to anchor the footing. Shape the footing wider at the bottom if you can. Re bar wired in as well. I bought bags of concrete from Bunnings and mixed two bags at a time in a big bucket and poured it in the hole. I used over fifty bags to build concrete right to ground level and fill the pier form. I was making a concrete pier so the form went on top of the footing pour, after allowing to set enoigh to support it. Reo down the form and into the footing , make sure its vertical and brace if necessary. Pour to top and set the hold down bolts in the top concrete. Bunnings sells concrete anchor bolts (M12) with long L shafts. Keep it damp; while it cures, allow at least three days to cure.

Mix the concrete next to the footing hole so you don't need to haul wet concrete up the hill. I used a hand truck to move the bags of concrete up to the site a few at a time.
You want all the concrete mixed to the same consistency, not to wet, just wet enough to pour. I mixed mine with a long section of rebar to get all the dry clumps mixed. It's hard work no hiding that but it can be done.

Equally hard was hand diggng all the obs post footings. It can be done, just take your time and get help if you need it.