I’ve done a few so far. I use small bottles of art resin (bit more $$ per gallon, but much easier to handle) and I don’t need much for filling in designs… easier to handle means less waste so I like to think the $$ difference is not too bad… as compared to, say, those river tables that are popular on youtube that take a lot of resin.
If you’re new to this, definitely go for small bottles, something like https://smile.amazon.com/gp/product/B07BM9LHRB/ and avoid gallon jugs 
Few basic things
- Resin needs a reasonable working temp (room temperature at least) to work, but also is best done in well ventilated rooms since it does off-gas some. Depending on where you are, that gets harder in winter… but really pay attention since if the temperature in the room is too cold, it won’t set fully and the work gets ruined
- Get some disposable graduated (e.g. with measurement lines) cups… easiest way to make sure you get the right (matching) volumes of resin and hardener
- Always poor in the hardener first, resin second
- If you put both bottles (before putting it in the cup) in a bit of hot water (to get it warm) before pouring it in the cup, the resin gets MUCH easier to poor/stir/handle and you also get less bubbles
- Use gloves/safety glasses.
- Stir. Stir. There is no over-stir, only under-stir. Use like a popsicle stick or similar to stir and assume you throw it away afterwards If you want to put some colored powder in, do this towards the end of your stir time (time is in the instructions of the resin). With Halloween coming… one special fun item is glow-in-the-dark powder.
- You will get bubbles. Do not freak out too much about this (you will get fewer if you heated the bottles up). See 8) for solving that
- Have a heatgun (or hair dryer) ready and assume that in the first 20 minutes after you do the poor into your artwork, you use this every 5 minutes to “pop the bubbles”. It will also cause bubbles to rise and pop. This step is essential to get crystal clear poors. Some videos say you can also use a propane torch. You can. But open flames… I like a heatgun better…
- Wood will create some extra bubbles (due to the air in the material). One trick is to poor a little bit first, use a brush to cover all surfaces, and then use the heatgun immediately to get the bubbles out. Once you’ve done that, THEN poor the rest. To be honest, I almost never do this and as long as I do step 8) enough it’s been fine… but for perfection, do this.
- Overpoor. Resin shrinks a bit as it sets, if you were to poor exactly to your vcarve/pocket line… it’ll end up below that once it is set. I usually poor too much, and then later use an orbital sander to get rid of the excess… but at least I get nice flush transitions that way. Don’t go overboard either though… WAAAY too much means you’ll end up sanding forever.
- Level. Resin is like water… make sure your work piece is level before you poor! (also have something underneath it that isn’t to the edges of it, so that you don’t glue to work to whatever it is resting on. similar to what you’d do when painting)