Learn how to make seamless patterns in Photoshop. If you have a pattern image, ensure the edges align perfectly. Open the file in Photoshop, go to Edit > Define Pattern, name it, and save. To use the pattern, open a larger document, create a new layer, paint it any color, click on FX, choose Pattern Overlay, select your pattern, adjust the scale, and click OK. Source: https://www.youtube.com/watch?v=I0MTqKKPlho

Using patterns to fill objects is a common feature in graphic design applications, including Affinity Designer. However, the approach to pattern fills in Affinity Designer differs from other tools like Inkscape and Adobe Illustrator. This tutorial demonstrates how to create a seamless pattern design and how to apply it as a pattern fill in Affinity Designer. Source: https://www.youtube.com/watch?v=V88GZ5fjlY4

Instead of repeatedly placing images or patterns, learn to seamlessly create a tile in Gimp. The tile filter makes it easy to achieve a clean repetition for your designs. Source: https://www.youtube.com/watch?v=eYFuw1Cs1_Y

A seamless pattern is an image that can be repeated without visible seams. By duplicating this image, you can create a pattern that extends infinitely for unique backgrounds. Wondering how to make these patterns? You can use any graphic design app or software, but today we'll use Canva - it's easy and free! :) Source: https://www.youtube.com/watch?v=Ee06gv-0oAo

Generate a seamless pattern that can be repeated infinitely with Inkscape. Source: https://www.youtube.com/watch?v=Dgsm-aqKcVs