The Isla pinafore style dress is crochet from the waist down, then joining yarn to create the bib and straps.

Written in US terms with abbreviations for UK terms.

Materials
90g dk/light worsted/ 8ply yarn for sizes preemie / newborn
110g dk/light worsted/ 8ply yarn for size 0-3 months
150g dk/light worsted/ 8ply yarn for size 3-6 months
180g dk/light worsted/ 8ply yarn for size 6-12 months
220g dk/light worsted/ 8ply yarn for size 1-2 years
4mm hook
2 x 15mm buttons

Gauge Square
With 4mm hook
Row1 Ch12, dc in 4th ch from hook and each chain across. (9) Turn
Row2-4 ch1, dc in base of ch1, dc 7. (9) Turn
Square should measure 5 cm wide by 5 cm tall.
If you’re out with a 4mm hook try 4.5mm hook.
If you have problems hitting the length this is not too important, as measurement will be given to follow.