The explanations that I will give you concern the technique I designed to make the hat, much simpler than other explanations you will find on the web, they do not concern the measures of the hat which, as you know, depend on the size of your head. To establish the size of the needles, the number of stitches to set initially and the centimeters in height, you will need to refer to other tutorials, or already have a clear idea of the size to be made.
OK, that said, let’s get started!
The first thing to do is to get some circular needles of the right size for the wool you are going to use.
Then assemble 3 stitches and knit a cord with the method shown in the video

Practically 3m are mounted, worked right and back to work from the first st worked, without turning the needle but by sliding the sts back towards the beginning of the row, bringing the yarn behind the work. In the video, two blunt needles are used, but you can safely use circular needles, sliding the stitches from one point to the other.
A tip: if you use a particularly fine wool, the cord can be made with 5 stitches, however the number of stitches must be odd.
Calculate a drawstring to measure the circumference of the hat (if you have a circumference of 50cm for example you will need to make a 50cm icord).
Close the cord and, again with circular needles, take 71 stitches (or whatever you need) from the edge. This is the only point where you have to get back to work.
Knit the first round inserting 3 markers: the first at the beginning of the round, the second after 13 stitches (calculate the number for the part of the cap without the border) the third after 28 stitches.
On the next round knit the stitches up to the third marker, then continue in garter stitch following the following pattern with shortened stitches between the two marker stitches, remembering that in the following pattern all rounds will be knit.
Work a trial sample for short rows.

If you don’t know how shortened needles are made, these pictures could help you.

ferrs shortened to straight
If by hypothesis we have to work 10 stitches and then we have to turn the work, we do this: we work 10 stitches, we pass the eleventh stitch on the right needle (Figure 1) we bring the yarn forward, we go over the stitch on the left needle and bring back the thread of the work (figure 2) we turn the work and continue to work. When in the following rows you find yourself working the point where you made the wrap & turn you have to do it in this way, insert the right needle taking the stitch to be knitted together with the turned one (figure 3) as if it were a single stitch.
Do not work the whole row, but only the stitches between the two markers, thus obtaining the curve of the cap.
At the end of the last short row, continue on all the stitches with the wool of the other color, making a rice stitch (two straight, two purl for two rows; then two purl and two straight …). After about 3 cm, pick up with the initial color and continue for 15cm (or whatever you need) before starting the decreases for the cap.
Use 5 markers to identify the decrease points, which you will make with a simple crossing followed by two stitches worked together.
When the cap is of the desired size, in the last round take two stitches at a time thus obtaining 12 stitches. Cut the thread very long and with a wool needle take the stitches from the needle and close the cap.

The hat is finished without any problems.