Gorilla All Purpose Wood Filler, Natural Finish, 16 Ounce Tub (Pack of 1) - Water Resistant for Indoor or Outdoor Projects and Repairs

https://a.co/d/03jbKrdv I would use exterior wood puddy. I would shove fiberglass insulation into the cavity and then top it off with wood puddy. Let it dry. Fill in any cracks.. wait for it to dry. Sand it. Paint it... then move on with life. It will maintain the look of the exterior wood siding. Caulking is cheap and nasty. It also fails fairly soon. This will take longer to do. But it will look so much better.

That's workable. Remove the tiles. Clean it with a vacuum hose. Sand it down. Clean it again. Don't worry about painting it, but you can if you want. Especially the inside outer walls. You'll need painters plastic to lay out over the ground to protect it from resin. I would strongly recommend silicone caulk, either this one or the traditional if you have a caulking gun. You want to caulk those seams in the wood (the one going across and around the inside edges). Smooth and scrape with your finger so there is only caulk in the cracks. Let the caulk dry. If you are going to paint, now is your chance. I also use wood filler to seal cracks. Your choice. I use a pigment paste, choose your desired color, for the bottoms of my tables and counters. Don't add more than 10% of the resin volume. Scoop a small amount in and mix it until it is opaque. Go with Let's Resin Deep Pour (calculate the volume you need, Radius² x Pi x Depth, add 20-30% for testing and mistakes). It is beginner friendly. 80 minute work time. Slow cure to reduce cracking and over heating. Naturally releases bubbles easily. 2:1 mix by volume, not weight. Has a great anti yellow formula! Use PPE as a preventative to safeguard your health. Using something like a painter's stir stick and a large measuring cup. Mix up ~500 ml of resin (example 340 ml part A + 170 ml part B). Stir it slowly and deliberately for 5-10 minutes (because you are a beginner and the number one mistake beginners make is not mixing the amount right and not stirring thoroughly). Scrape the sides of the cup, bottom of the cup, and both sides of your stick frequently. Using a clean stick, add the desired amount of pigment paste. Don't use the resin covered stick to scoop up the paste. Stir it until blended. Pour this all over the wood. Once it is empty, use the stick to smear the resin over the wood, covering every inch. If you need more, make more. But we are only sealing the wood at this point. We are also testing for any leaks. So, don't over do it. Depending on the temperature of the environment, it could gel in 8 hours or 24 hours. You'll want to wait till it is tacky. Check for leaks. Plug the leaks. Once tacky, use your measurements to figure out how much resin you'll need for about 1/8 inch deep resin. Mix it up accurately. Stir thoroughly. Add your paste. Scoop the resin with the stick to check how pigmented it is. As it spills back into the bowl it'll either be clear or dark. Pour it in once you are ready. Wait till it is tacky. Check for leaks. Looks way better than painted backgrounds. Especially since paints can bubble or wrap due to resin. From here, it depends on your final look. With a tacky bottom layer, you can place items and they won't drift (much) with the final pour. You can get inks, mica powders, glitter, or whatever you wish. Use clear. Whatever your plan is. The deep pour resin could take up to a full week to cure. Be patient. Deep pour resins are not as viscous as coating resin. Meaning, they don't dome well. Resin tends to shrink as it cures. Pulling towards the center of the volume. Most of us that do tables know we have to sand and polish them. A short cut is to get coating resin to finish the piece. Roughing the smooth resin and then flood coating the entire table to get it perfectly level. You'll have to decide which way you want to go. Hopefully this doesn't discourage you. 🤣 I would recommend holding off until the warmer months. The colder winter causes resin to take longer to cure. Sometimes even causing it to fail. In doing so, gives you plenty of time to save up and test and play. Watch YouTube tutorials.