I'm trying to learn how to build a deck in Anki so that I can improve my play by creating positions that I need to learn and by improving tactics. I'm looking for a guide on that process.
Well, what exactly do you want to know? The essentials are very simple: Have a "front side" showing a tactical position and a "back side" showing the answer. For the former you can just use images taken from scans. But there's also a note type available for Anki which lets you store positions in FEN notation. Search for "chess" on AnkiWeb to find it. This method is more memory efficient (and in some cases looks better), but might require a little more work than images, unless you also have the puzzles in e.g. PGN format.
I started out as an absolute beginner a little less than a year ago. I'm still a beginner and at the very bottom of food chain in the chess club I joined recently, but compared to from where I started I have improved a lot.
In my informed opinion spaced repetition in learning chess aims at pattern recognition. In other words: It's not about actually memorizing the solutions (so don't bother creating very short repetition circles), but developing an intuition for where possible solutions might be. In effect, though, it trains tactical intuition more than calculation. So I find that I need to compliment my Anki training not only with actual play, but also with solving composed mate-in-2 puzzles that I set up on the board to improve my board vision and calculation ability.
The specifics of what types of puzzles/questions are suitable depend on your level of play. As always with spaced repetition the cards should have clear, unambigous, easy to state answers. Though what exactly constitutes a "clear, unambigous, easy to state answer" probably differs from person to person and today I find solutions clear that were confusing to me a year ago. That being said, at my level basic tactics still work best. I gave up on creating more strategic cards for now, until my abilities have improved.
I guess that, since this is about pattern recognition, it matters what book you are using. I'm using Susan Polgar's tactics book for tactical motifs and the mate-in-two puzzles from L. Polgars 5000-something book for piece-interaction, mating patterns etc. Since solving puzzles on your smart phone is a great way to pass the time in the subway, I also have a deck with beginner puzzles from the 'Manual of chess combinations': unlike with the other two, I don't put any pressure on myself to go through this deck every day, but use it only when I want some 'extra chess'.