Place the thread over the object to be tied. 

Pass the working end underneath the object being tied

Take the working end across the thread.

Take the working end under the object you are tying

Take the working end under thread which went above the object which you were tying

Pull the ends tightly to form the knot.

This shape is made by laying one straw horizontally and a second straw vertically. Use a clove hitch to tie a piece of cotton to one straw. Take the end, in a circular motion, over one straw, under the next, over the next, under the next etc. Continue until the straws hold firmly in a cross shape 

Make a number of these.

In the same under and over manner used previously, two shapes can be joined to look like this.  
This can be used as the centre for a star, with long spokes of straw threaded into each end of the star/hub

Joining two of the previous shapes together will form this rosette shape

Simple variations can be made by cutting the straw ends. Here they have been angled

In this shape a small triangle has been removed from each end. 
Experiment with different cuts, vary the size or number of straws.