Watch the III - IV - II - I Phrygian online guitar lesson by Robbie Calvo from Modal Expose
Modal progressions can be as simple or as complex as you want them to be, that is your choice, just remember to make them musical.
This Phrygian progression is pretty simple, intentionally so, because I want you to be able to hear the tonal center without wading through a plethora of chords and voicings.
I'd like you to play through this chord progression, name the chords and the scale position they occupy and then write a couple of grooves yourself. Some of you will find this easy to do and others will struggle with it. I will tell you this, writing modal progressions isn't as easy as you might think. Stringing chords together is one thing, making them palatable to the ears is another. Your challenge is to understand the modality and then be able to get creative with it - go forth and write modal music!