Easy boards are graded by replay: our solver completes every one of them using only the entry-level techniques — magic blocks (clues with a single possible digit combination, like 4-in-two = 1+3), simple across/down intersections, and finishing a run's last empty cell by arithmetic. If a board needed anything deeper, it did not land in this bucket.
That grading means an easy board never demands long pencil-mark bookkeeping: there is always a cell somewhere whose value follows directly from one clue pair. The skill being trained is finding it.
Start with 4 × 4 boards if you are brand new, and keep the combination reference open — recognizing magic blocks on sight is what makes easy Kakuro fast.