There are many Vector Graphics (Inkscape) and CAD (FreCAD) programs that are designed for working with 2D shapes with ease and great precision.
Unfortunately, Blender does not have the strongest 2D toolset but still can do the job via:
importing the 2D file formats with your blueprint as Curves (.svg, dxf, etc)
using the available modeling tools.
We will use the capability of the Blender's 2D Curve to have holes using smaller shapes inside a bigger one. Note that in order for the holes to appear the small shapes must have an opposite direction than the big surrounding shape.
You can import your blueprint as an Empty of type Image and trace the lines of your design from Top View starting from a single Mesh vertex:
Notice that only edges and vertices are used (no faces)!
Once complete - convert the Mesh to a Curve object (Right Click on the Mesh in Object mode and select Convert To > Curve. By default the type of the Curve is Poly, but it can be changed to Bezier if curved segments are needed:
Go into your Curve Data properties (located in the Properties Editor)
and set the Shape to 2D and Fill Mode to Both. This will automatically fill the curve and show the inside triangles as holes. In case you don't see a spline as a hole that means its direction needs to be reversed (select the spline and go to 3D Editor menu Segments > Switch Direction):
As additional final step you can extrude the 2D shape. Go to the Curve Data and give Geometry > Extrude parameter a value to your liking.
I am not going into details how to use the Mesh modeling tools but I strongly recommend learning more about Meshes, Curves and Snapping options in the Blender' manual. Also you are welcome to ask further questions.