Create a Photoshop Action:

Move the Horizontal and Vertical sliders. A good rule of thumb is to offset by exactly half of your image dimensions (e.g., if your image is 1024x1024, set the offset to 512 for both).

The Pattern Maker will create a seamless pattern from the image, which can be used as a texture.

Go to Edit > Define Pattern. Name your texture and click OK. Create a new, much larger document (e.g., 3000x3000px). Create a new Layer and go to Edit > Fill.

When creating seamless textures in Photoshop, there are several best practices to keep in mind:

The Spot Healing Brush is the fastest method. Simply paint over the visible lines, and Photoshop will use its Content-Aware technology to blend the pixels. For more control, use the Clone Stamp Tool (Alt+Click to sample an area, then paint over the seam). This allows you to manually ensure that patterns or grains match up naturally.