So, I had actually started making myself some flash cards when I came across this site last week.
The site is the home of a program called Anki, and it’s available for most operating systems & phones. You can make your own flash cards with this program, or download any from hundreds of pre-made decks that others have uploaded.
I’ve only had a brief look so far, but I downloaded (on my phone) one of the pre-made basic Japanese decks. It showed a card on my screen with a Japanese word written on it in Romaji, and it had a voice say the word as well. At the bottom of the card was a button to show what the word meant. When you press the button the translation is shown, and a new set of buttons are shown giving you the options to review this word again in a few minutes, tomorrow, in a few days, or in a week (you pick whichever one you think you need based on how much trouble you had remembering the words meaning).
There’s a link to the demo video on youtube so you can see for yourself.