A one day hat, using a borrowed block from Nina. This block, dating probably to the 50’s, belonged to a milliner from Barcelona.
The challenge with this block is managing to get the creases well marked. I’ve used reed for this purpose, precut to the right length I have used pins to keep it in place, stretching to make sure the felt is flat.
To prepare the felt I’ve sprayed the interior with water and microwaved it for 1 minute (wrapped in a cloth). Then I’ve brushed the inside with ecologic sizing (that smells of white glue) and put it back for a minute in the microwave, all wrapped up. By the way, never put flammable sizing in the microwave unless you want your house to explode! After this process the felt is really soft and the steam has gotten to the core of the felt (you can also turn the felt inside out to make it easier to size and spray).
Once smoking hot I’ve pulled the felt over the block (previously covered with plastic wrap), calculating for more felt on the front where the creases go (and the flap under is larger). After that I’ve started pinning the reed on the creases (with hardened steel pins using a small hammer). Here are some pictures (out of focus… sorry!):

The one worry here is the fact that the felt will be marked by the reed, but fortunately the marks have disappeared after some steaming (using my kettle, I never put the blocks in the microwave) and brushing (with my brass brush, that I’ve noticed has a sticker saying it’s a jewelery brush, which must be softer than the bbq cleaning ones).
The underside rim is part of the finished hat and is not to be trimmed away. It’s important that it remains flat, so after pinning it I added a piece of reed all around to make sure it would look neat.
To keep the shape of the crown top I have used a small fabric bag filled with marble powder (the powder purchased at an art supplier, the bag made by Nina). It’s really heavy and it adapts to the shape, but because some dust comes out it’s necessary to put a cloth between the felt and the bag.
My air oven allows for very low temperatures, so I set it to 50ºC (32ºF) and put the block inside for a couple of hours. Half way through I took out the marble dust bag so that the top would dry completely.

Once dry I took out the pins with some heavy duty pliers, gave the felt some steam and a brush, and then trimmed the excess felt from the underside using a cutter (carefully avoiding to damage the block). Then I coaxed it out of the block, which was a bit stressful because I had to stretch the edge a little so it would pop out. Fortunately it was not too bad and folded back in without any deformation.
Will post pictures of the finished had soon!