Italic lettering derives from the Roman and as it began to be written at speed, so it naturally began to slope to the right and the characteristic wedge shapes which define italic writing, began to emerge. The degree of this slope is fairly flexible. It is generally accepted that anywhere from 5 to 15 degrees is all right - further than 15 degrees and the lettering begins to topple over and distort.
I base my normal italic on the proportions of the letter ‘n’ being 8 : 6 (8 being the height of the letter) written at a slope of 8 degrees from the vertical. At these proportions, the characteristic wedge shape of italic lettering is formed at a slope of 40 degrees from the vertical. If this 40 degrees slope is then applied to the ligatures, the two sets of parallel lines are produced - one by the 8 degree slope of the writing and the other by the slope of the wedge shapes and the ligatures.
Including the base line, there are then 3 sets of parallel lines i.e. base lines, writing lines at 8 degrees and wedge/ligature lines at 40 degrees. I find this balance to be symetrical, easy to write and legible. This formation, produced as a grid provides the basis for practice. In time, as the lettering becomes natural, the grid can be dispensed with.
If a different slope to the lettering is preferred, then adjustments can be made. For example, if the writing slopes at 12 degrees, then the ligature/wedge slope is 44 degrees to maintain the shape of the lettering.
If lettering which is wider or narrower is preferred, then compensation for the change of proportion has to be made.
The important point is that the three sets of parallel lines should be adhered to.
This is only one approach to writing italic, but it works well. As a skeletal base, this structure forms a strong basis on which formal italic or personal handwriting can be built.
