Good luck for teaching yourself A level chemistry! I'm teaching myself A level maths this year. I did Chemistry for A level, and I found it a really fun subject, though you're definitely going to put in the time and make sure you do lots of practice questions if you want a good grade.
For chemistry, I would recommend flashcards after question/exam practice with notes from the questions, since there are a lot of questions in chemistry that have a similar style, and if you learn the style of question it'll become much easier to answer them all.
Physicsandmathstutor.com has a lot of chemistry resources on it, as well as a complete collection of chemistry papers. Studymind is also useful, though both sites contain a lot of overlap in the questions they have since there's only so many questions that they can ask.
When you come across a question you don't understand in a paper, I'd recommend seeing whether there's a youtube video of someone explaining how they did in the paper, so that you can learn from them showing you how to approach the question.