One area which was not covered in the original Old School Hack (OSH) rules, probably because it was a beta version, is how characters create magic items. Now I figure an easy way to handle magic items for OSH is to treat magic items simply as objects with talents and/or attributes, a sort of "inanimate character" one might say. So you could have a Swashbuckler's Sash which grants the wearer +1 to Daring rolls, or a Parrying Dagger which grants the wielder the Fighter's Parry talent. An object can have multiple attributes and/or multiple talents.
Each attribute bonus of +1 and each talent could be considered a "level" for the object. So you add up the "levels" and that's how much work and expense it takes to make that object. Now, most talents are more powerful than a +1 attribute bonus. However, many talents are not continuous and thus their power is moderated. But for simplicity let's just stick with everything being worth one level for now.
Then let's consider that making magic items usually includes materials, rituals/crafting, and possibly tools/equipment. The materials and equipment can be mundane or magical. In some cases specifically magical materials or equipment might be required. But OSH is all about elegant simplicity so we don't want to get bogged down in a lot of detail and record-keeping. One simple way is just to say that X gold pieces worth of materials and equipment are needed, expended over X days or weeks of crafting, to create an object of X levels. This approach is simple and also makes it easy for DMs to regulate the ease of creating magic items in a campaign by altering the cost and time required per level. But a drawback of this approach is that it is rather boring. It's more like accounting than role play gaming.
I'd like there to be various magic item creation talents, a bit like the item creation feats in D&D 3rd Edition. Having several allows character specialization and adds flavor. But for simplicity let's just have one generic one for now, Arcanist:
Arcanist/rested-focus: Summoning forces beyond the ken or ordinary mortals you pour magic of your choosing into crafting materials to prepare them for fashioning into an object of arcane power. Each arcanist performance requires the expenditure of 100 gold coins worth of supplies.
Each level of attribute or talent in the object requires the inclusion of six fully "arcanized" materials. (I'm just grabbing six here to mirror that there are six talents per class, six domain talents per deity, etc. This number is adjustable by the GM to fit the desired power level of the campaign. Six is just easy to remember.) Special very rare materials, such as mithril, count as two common materials. Each material must be arcanized six times to "set" the magic into it. The crafter of the item may arcanize into it any of the six character attributes (Brawn, etc.) but only up to a maximum of a bonus of +6. The crafter may also arcanize in any talent personally known (GMs may place limits on certain talents).