To avoid the fullness of many stitches in corners of solid squares and to avoid large open holes, I finally sat down and came up with -
Centre as in the previous no-hole square: 4 groups of 3 tr (UK or dc US), separated by ONE chain into a magic ring.
Rnd 1 - 1 tr (UK) into each tr, 1 tr into the cnr ch NOT into the ch sp, 1 tr into the body of the tr just worked, 1 ch, 1 dtr (UK - yoh twice) into the same ch st, 1 dc (UK or sc US) into the body of the dtr just worked* Rep to end of rnd.
Continue this round to desired size.