An integrated microcircuit, in which all the elements are made on one crystal, is impossible to make on your own. Only the so-called hybrid schemes are available to the home master. Using SMD components, they can also be made very compact.
Find on the schematic diagram of the device that you want to build on the basis of a homemade hybrid microcircuit, a section consisting only of low-power transistors and resistors, as well as small capacitors (no more than a few hundred picofarads). This section should have as few points as possible for connecting to the rest of the parts - after all, this is exactly how much the microcircuit will have.
Draw a separate diagram of the internal structure of the microcircuit. Assign numbers to its pins, when choosing the numbers of which, be guided by the convenience of assembly (there should be as few intersections of conductors without connections). Also, separately draw a diagram of a device based on this microcircuit. Designate the latter as a rectangle with pins, the numbers of which coincide with those indicated in the previous diagram.
Assemble the electronic filling of the hybrid microcircuit in a convenient way - on a miniature printed circuit board (including a universal one) or by volumetric assembly. Be sure to use only SMD components - just one ordinary part can significantly increase the dimensions of the structure. It is possible to reduce the density at the cost of some increase in volume by making the hybrid microcircuit multilayer. In this case, it is important to ensure the impossibility of short circuits between the layers using insulating gaskets.
Use a flat, round box made of insulating material for the housing for your DIY hybrid IC. In the lower part of it, make as many cuts as the output microcircuit has. After placing the assembled structure in the case, pull the leads through the cuts, then reinstall the cover and glue it with Moment glue or the like. To avoid the ignition of glue vapors, do not solder or use the microcircuit until the seam is completely dry. Unlike a modern monolithic microcircuit, a hybrid one can be opened, repaired and glued again in case of failure. But the degree of integration is extremely low by modern standards.