First the approach, or generic answer, then the specifics in your question.
I will answer for OG V5.4.4, which is what I use. I am sure the current release has the same facility, but the GUIs have changed, you just have to figure it out.
In the ColourPicker, the sixth icon (method) provides the Fill Patterns.
I will assume you have gotten this far (with the equivalent GUI in the current release):
It has a variety of patterns (left)
with a choice of colour for foreground/background
with a ColourWheel for each (Saturation, Opacity)
red foreground and blue background shown for contrast
the fixed set of patterns on the left, which include different distance between the items in the patterns
changing the Saturation/Opacity on the Colours, such that I emphasise this or that, in order to obtain the effect that I want
The dots and crosses and diagonals are already there in the Fixed Set of Patterns, but with fixed distance between the items, therefore, in the first instance, use that.
2 Make a Pattern File
If you want something beyond that … which really means dots or crosses or anything, of (a) a particular size, and (b) a particular distance between, I would:
make a pattern file
you have total control of the Shapes; Fill; Stroke; position; etc
eg. I have used stars, with a particular size (3.6 x 3.6cm), and a distance between that is staggered
eg. a large canvas size (this is A2 or 17 x 22in for our American friends), because want a reasonable size when drawing; positioning; etc, but we will reduce it when we use it