From experience, I can say that self-adhesive products work poorly on fabric. There are options available to you in the form of sew-on hook-and-loop fasteners that you would apply to fabric using liquid glue made for fabric.
A quick search for fabric adhesive resulted in a number of products of varying specifications. Some of the results, in question-and-answer form specific to different products indicated temporary adhesion and permanent adhesion, indicating that you can select the duration of your item's durability in that respect.
Another aspect that appeared in the search results was flexibility listed as a feature. I would be suspect of a product that did not list such a feature as being undesirable.
One product which appears well suited to your application is Fabric-Tac, a permanent flexible liquid that lists as being suited for leather, wood and lace. Leather is notoriously difficult to secure, as its flexibility frequently destroys any bond. Fabric-Tac lists at a bit more than eleven US dollars on Amazon for four liquid ounces. It seems like a small amount of product for a large amount of money, but the amount you use is likely to be quite small.
If you've read of iron-on hook-and-loop fasteners, it's possible that they are coated with heat-activated fabric adhesive. One such product is available on Amazon, called Therm O Web SpraynBond Fusible Adhesive Spray. It is priced lower than the liquid adhesive, but spray applications often results in higher levels of waste due to overspray.
Another search specific to iron-on application resulted in many false leads to coin/dot form, but a few tape and strip versions, almost exclusively Velcro™ brand products.