Right, now having blown your brain cutting impossibly shallow angles for the upright dividers (I hope it wasn't that bad - I "borrowed" my husband's professional shed-making machinery so I cheated)... now here's an easier bit of woodwork for you.
The battens you attach to the uprights are to hold the cladding in place, and should measure 25mm x 25mm, though I couldn't find that at my local branch of Wickes so settled for 25mm x 38mm. As you can see from the pic you only need them along the top edge and down the two vertical sides of the dividers - not along the bottom. You'll obviously need the battens on both sides of the two central dividers.
You do need to cut the top batten to shape at an angle, but it's a lot easier this time. Use the edge of a bit of cut-off batten wood as a spacer to work out how far down you need to attach the batten itself (if you're using 25x38mm wood, use the 25mm edge). Just line the spacer up with the top edge of the divider and draw a line underneath. This marks where the top edge of the batten will go.
Then cut the batten to about 10cm (4") too long at each end and nail it on so that it lines up with the mark. After that, it's just a matter of cutting the ends off flush with the divider.
The upright battens are far easier - unless you're a real perfectionist (or are borrowing your husband's shed-building machinery) you don't need to cut the ends at an angle as they go in pretty close anyway, certainly close enough to fix the cladding to. You do still need to do the thing with the spacer, though, or the cladding won't lie flush with the uprights.
After you've done all that, you'll also need to put in an extra bit of battening all around the inside edge of the two end dividers - the divider in the picture is an end divider, so you can see how I've done this if you look closely. This is so that you can attach the cladding across them to form the ends of the coldframe. Again, you don't need to be too exact - just cut the battens off straight and fit them in as snugly as you can.
I'll get on to cladding the ends next time, and all this will hopefully start to make a bit more sense.
In case you missed the previous bits of this inordinately long series, here they are:
How to make a coldframe #2