String blocks are pretty forgiving, but after doing a few blocks I decided that it would help to draw a dark diagonal line on the block foundation to help center that first string.
Next go to your string bag and pull out a pile of scraps. If you want, you can control the colors or just pull scraps at random. For this group of blocks, I just tried to pull brights. I did cut black strips at 1 1/2" to make a strong diagonal line that was consistent down the center of each block.
Press open either with your iron or finger press.
Now comes the fun part. After you have a pile of blocks you can have fun designing your quilt.
Here is one setting.