Place Blocks In A Grid In-Game

Hello. I am having this problem. I have experimented with many different setups, none of them working yet.

My goal: Be in game and place cubes on a grid as in minecraft.
My problem: Getting the grid set up.

I already set up a line trace so that the block can be placed anywhere, but I want it to snap to a grid, rounded to 100s (because the blocks are 100 units wide) so is there a way to do this at least semi-simply? I have seen a few posts but couldn’t find any with a good well-explained solution. I figure modulus and/or rounding will help here?

Thanks in advance.

I’m using a similar system in my project, though I’m only building blocks on a planar grid, meaning I don’t build blocks on top of eachother like in Minecraft, but I imagine one could adjust the system to work that way.
Looking at my blueprints I don’t think there’s a really simple way, but I built my system from a tutorial project I found on Youtube, you could download it and see if you can figure out how to use it for your game.

Link to the video.

The download is in the video description.